prank (n.) Look up prank at Dictionary.com
"a ludicrous trick" [Johnson], 1520s, of uncertain origin, perhaps related to obsolete verb prank "decorate, dress up" (mid-15c.), related to Middle Low German prank "display" (compare also Dutch pronken, German prunken "to make a show, to strut"). The verb in the modern sense also is from 1520s. Related: Pranked; pranking.
prankster (n.) Look up prankster at Dictionary.com
1927, American English, from prank + -ster.
praseodymium (n.) Look up praseodymium at Dictionary.com
rare metallic element, 1885, coined in Modern Latin by discoverer Carl Auer von Welsbach (1858-1929) from Greek prasios "leek-green" (from prason "leek") + didymos "double," the name given to an earth in 1840, so called because it was a "twin" to lanthana. When didymia was further analyzed in the 1880s, it was found to have several components, one of which was characterized by green salts and named accordingly, with the elemental suffix -ium.
prat (n.) Look up prat at Dictionary.com
"buttock," 1560s, criminals' slang, of unknown origin. Later in U.S. criminal slang, "hip pocket" (1914), and in British slang "contemptible person" (1968).
prate (v.) Look up prate at Dictionary.com
early 15c., from or related to Middle Dutch praten "to chatter" (c.1400), from a Proto-Germanic imitative root (compare East Frisian proten, Middle Low German praten, Middle High German braten, Swedish prata "to talk, chatter"). Related: Prated; prating. As a noun from 1570s.
pratfall (n.) Look up pratfall at Dictionary.com
1939, from prat "buttock" + fall (n.). "Chiefly N. Amer. slang" [OED]. As a verb from 1940.
Pratt Look up Pratt at Dictionary.com
the surname apparently is from Old English *prætt (adj.) "cunning, astute;" related to late Old English noun prætt "a trick" (see pretty). As a type of pottery, named for Staffordshire pottery manufacturer Felix Pratt (1780-1859).
prattle (v.) Look up prattle at Dictionary.com
1530s, frequentative of prate (q.v.). Related: Prattled; prattling. The noun is attested from 1550s.
pravity (n.) Look up pravity at Dictionary.com
"depravity," 1540s, from Latin pravitas "crookedness, distortion, deformity; impropriety, perverseness," from pravus "wrong, bad," literally "crooked."
prawn (n.) Look up prawn at Dictionary.com
early 15c., prayne, of unknown origin. "No similar name found in other langs." [OED].
praxis (n.) Look up praxis at Dictionary.com
1580s, from Medieval Latin praxis "practice, exercise, action" (mid-13c., opposite of theory), from Greek praxis "practice, action, doing," from stem of prassein, prattein "to do, to act" (see practical).
pray (v.) Look up pray at Dictionary.com
early 13c., "ask earnestly, beg," also (c.1300) "pray to a god or saint," from Old French preier "to pray" (c.900, Modern French prier), from Vulgar Latin *precare (also source of Italian pregare), from Latin precari "ask earnestly, beg, entreat," from *prex (plural preces, genitive precis) "prayer, request, entreaty," from PIE root *prek- "to ask, request, entreat" (cognates: Sanskrit prasna-, Avestan frashna- "question;" Old Church Slavonic prositi, Lithuanian prasyti "to ask, beg;" Old High German frahen, German fragen, Old English fricgan "to ask" a question).

Parenthetical expression I pray you, "please, if you will," attested from 1510s, contracted to pray 16c. Related: Prayed; praying. Praying mantis attested from 1809. The "Gardener's Monthly" of July 1861 lists other names for it as camel cricket, soothsayer, and rear horse.
prayer (n.) Look up prayer at Dictionary.com
c.1300, from Old French prier "prayer, petition, request" (12c., Modern French prière), from Medieval Latin precaria "petition, prayer," noun use of Latin adjective precaria, fem. of precarius "obtained by prayer, given as a favor," from precari "to ask, beg, pray" (see pray). Related: Prayers.

Prayer-book attested from 1590s; prayer-meeting from 1780. To not have a prayer "have no chance" is from 1941.
prayerful (adj.) Look up prayerful at Dictionary.com
1620s, from prayer + -ful. Related: Prayerfully; prayerfulness.
pre- Look up pre- at Dictionary.com
word-forming element meaning "before," from Old French pre- and Medieval Latin pre-, both from Latin prae (adverb and preposition) "before in time or place," from PIE *peri- (cognates: Oscan prai, Umbrian pre, Sanskrit pare "thereupon," Greek parai "at," Gaulish are- "at, before," Lithuanian pre "at," Old Church Slavonic pri "at," Gothic faura, Old English fore "before"), extended form of root *per- (1) "beyond" (see per).

The Latin word was active in forming verbs. Also see prae-. Sometimes in Middle English muddled with words in pro- or per-.
pre-arrange (v.) Look up pre-arrange at Dictionary.com
also prearrange, 1792 (implied in pre-arranged), from pre- + arrange. Related: Pre-arranging.
pre-arrangement (n.) Look up pre-arrangement at Dictionary.com
also prearrangement, 1775, from pre- + arrangement.
pre-atomic (adj.) Look up pre-atomic at Dictionary.com
"before the atomic age," 1914, in "World Set Free" -- H.G. Wells anticipating the word the future would use to look back at a time defined by events that hadn't yet happened in his day; from pre- + atomic.
pre-date (v.) Look up pre-date at Dictionary.com
also predate, 1859, "to antedate, to assign an earlier date to," from pre- + date (n.1) "point in time." As "to exist before," from 1857. Related: Pre-dated; pre-dating.
pre-dawn (adj.) Look up pre-dawn at Dictionary.com
1940, from pre- + dawn (n.).
pre-eclampsia (n.) Look up pre-eclampsia at Dictionary.com
also preeclampsia, 1903, from pre- + eclampsia. Related: Pre-eclamptic (1896).
pre-elect (v.) Look up pre-elect at Dictionary.com
1560s, from pre- + elect (v.). Related: Pre-elected; pre-electing.
pre-election (n.) Look up pre-election at Dictionary.com
1580s, from pre- + election.
pre-electric (adj.) Look up pre-electric at Dictionary.com
1894, from pre- + electric.
pre-eminence (n.) Look up pre-eminence at Dictionary.com
also pre-eminence, c.1200, from Late Latin praeeminentia "distinction, superiority," from Latin praeeminentem (nominative praeeminens), present participle of praeeminere "transcend, excel," literally "project forward, rise above," from prae "before" (see pre-) + eminere "stand out, project" (see eminent).
pre-eminent (adj.) Look up pre-eminent at Dictionary.com
also preeminent, mid-15c., from Medieval Latin preeminentem, from Latin praeeminentem (nominative praeeminens), present participle of praeeminare "to transcend, excel," literally "to project forward, rise above" (see pre-eminence). Related: Pre-eminently; preeminently.
pre-empt (v.) Look up pre-empt at Dictionary.com
also preempt, 1830, "secure by pre-emtion," back-formation from pre-emption, originally American English. In the broascasting sense, it is attested from 1965, American English, a euphemism for "cancel." Related: pre-empted; preempted.
pre-emption (n.) Look up pre-emption at Dictionary.com
also preemption, c.1600, literally "the right of purchasing before others," from pre- "before" + emption.
pre-emptive (adj.) Look up pre-emptive at Dictionary.com
also preemptive, 1806, "pertaining to preemption;" from pre-emption + -ive. Specifically of an attack on an enemy who is plotting his own attack, 1958, a term from the Cold War. Related: Pre-emptively; preemptively.
pre-emptory (adj.) Look up pre-emptory at Dictionary.com
also preemptory, 1822, "relating to pre-emption," from pre-emption + -ory.
pre-engage (v.) Look up pre-engage at Dictionary.com
"bind in advance by promise," 1640s, from pre- + engage (v.). Related: Pre-engaged; pre-engaging.
pre-exist (v.) Look up pre-exist at Dictionary.com
1590s, from pre- + exist. Related: Pre-existed; pre-existing.
pre-existence (n.) Look up pre-existence at Dictionary.com
1650s, from pre- + existence.
pre-existing (adj.) Look up pre-existing at Dictionary.com
also preexisting, 1590s, past participle adjective from pre-exist. The medical insurance pre-existing condition is attested from 1942.
pre-law (adj.) Look up pre-law at Dictionary.com
"of or pertaining to study in preparation for law school," 1961, American English, from pre- + law (school).
pre-med (n.) Look up pre-med at Dictionary.com
"undergraduate student in preparation for medical school," 1934, from premedical. From 1941 as "a major in preparation for medical training." As an adjective from 1936.
pre-op (n.) Look up pre-op at Dictionary.com
1913 as short for pre-operative (preparation).
pre-order (v.) Look up pre-order at Dictionary.com
1630s, from pre- + order (v.). Marked in OED 2nd ed. as "rare." Related: Pre-ordered; pre-ordering.
pre-owned (adj.) Look up pre-owned at Dictionary.com
1961, American English, from pre- + owned. A euphemism for used.
pre-position (v.) Look up pre-position at Dictionary.com
"to position beforehand," 1946, from pre- + position (v.). Related: Pre-positioned; pre-positioning.
Pre-Raphaelite (n., adj.) Look up Pre-Raphaelite at Dictionary.com
c.1848, in reference to the "brotherhood" (founded 1847) of Holman Hunt, Dante Gabriel Rossetti, John Everett Millais, and others (seven in all) who, encouraged by Ruskin, sought to revive the naturalistic spirit of art in the age before Raphael Sanzio (1483-1520).
pre-record (v.) Look up pre-record at Dictionary.com
1937, from pre- + record (v.). Related: Pre-recorded; pre-recording.
pre-registration (n.) Look up pre-registration at Dictionary.com
also preregistration, 1901, from pre- + registration.
pre-release (adj.) Look up pre-release at Dictionary.com
1916, in reference to motion pictures, from pre- + release (n.).
pre-teen (adj.) Look up pre-teen at Dictionary.com
also preteen, 1926, from pre- + teen. As a noun, "pre-teen person," from 1962. Sub-teen (1944) also was used.
preach (v.) Look up preach at Dictionary.com
at first in late Old English predician, a loan word from Church Latin; reborrowed 12c. as preachen, from Old French preechier "to preach, give a sermon" (11c., Modern French précher), from Late Latin praedicare "to proclaim publicly, announce" (in Medieval Latin "to preach"), from Latin prae "before" (see pre-) + dicare "to proclaim, to say" (see diction). Related: Preached; preaching. To preach to the converted is recorded from 1867 (form preach to the choir attested from 1979).
preacher (n.) Look up preacher at Dictionary.com
c.1200, from Old French preecheor "preacher" (Modern French prêcheur), from Latin praedicatorem (nominative praedicator) "public praiser, eulogist," literally "proclaimer" (see preach). Slang short form preach (n.) is recorded by 1968, American English.
preachment (n.) Look up preachment at Dictionary.com
late 14c., "a preaching;" earlier "an annoying or tedious speech" (c.1300); see preach (v.) + -ment. Related: Preachments.
preachy (adj.) Look up preachy at Dictionary.com
1819, from preach + -y (2). Related: Preachiness.
preamble (n.) Look up preamble at Dictionary.com
late 14c., from Old French preambule (13c.) and directly from Medieval Latin preambulum, neuter adjective used as a noun, properly "preliminary," from Late Latin praeambulus "walking before," from Latin prae- "before" (see pre-) + ambulare "to walk" (see amble (v.)).