word-forming element of Latin origin meaning "bad, badly, ill, poorly, wrong, wrongly," from French mal (adv.), from Old French mal (adj., adv.) "evil, ill, wrong, wrongly" (9c.), from Latin male (adv.) "badly," or malus (adj.) "bad, evil" (fem. mala, neuter malum), from Proto-Italic *malo-, from PIE *mol-o-, probably from PIE root *mel- (3) "false, bad, wrong."

Most Modern English words with this element are 19c. coinages. It generally implies imperfection or deficiency, but often it is simply negative (as in malfeasance, malcontent). It is equivalent to dys- and caco- of Greek origin and Germanic mis- (1).

word-forming element meaning "forward, forth, toward the front" (as in proclaim, proceed); "beforehand, in advance" (prohibit, provide); "taking care of" (procure); "in place of, on behalf of" (proconsul, pronoun); from Latin pro (adv., prep.) "on behalf of, in place of, before, for, in exchange for, just as," which also was used as a first element in compounds and had a collateral form por-.

Also in some cases from cognate Greek pro "before, in front of, sooner," which also was used in Greek as a prefix (as in problem). Both the Latin and Greek words are from PIE *pro- (source also of Sanskrit pra- "before, forward, forth;" Gothic faura "before," Old English fore "before, for, on account of," fram "forward, from;" Old Irish roar "enough"), extended form of root *per- (1) "forward," hence "in front of, before, toward, near," etc.

The common modern sense of "in favor of, favoring" (pro-independence, pro-fluoridation, pro-Soviet, etc.) was not in classical Latin and is attested in English from early 19c.

late 14c., posen, "suggest (something is so), suppose, assume; grant, concede," from Old French poser "put, place, propose," a term in debating, from Late Latin pausare "to halt, rest, cease, pause" (source also of Italian posare, Spanish posar; see pause (v.)). The Late Latin verb also had a transitive sense, "cause to pause or rest," and hence the Old French verb (in common with cognates in Spanish, Italian, Portuguese) acquired the sense of Latin ponere "to put, place" (past participle positus; see position (n.)), by confusion of the similar stems.

One of the most remarkable facts in F[rench] etymology is the extraordinary substitution whereby the Low Lat. pausare came to mean 'to make to rest, to set,' and so usurped the place of the Lat. ponere, to place, set, with which it has no etymological connection. And this it did so effectually as to restrict the F. pondre, the true equivalent of Lat. ponere, to the sense of 'laying eggs;' whilst in all compounds it completely thrust it aside, so that compausare (i.e. F. composer) took the place of Lat. componere, and so on throughout. Hence the extraordinary result, that whilst the E. verbs compose, depose, impose, propose, &c. exactly represent in sense the Lat. componere, deponere, imponere, proponere, &c., we cannot derive the E. verbs from the Lat. ones since they have (as was said) no real etymological connection. [W.W. Skeat, "Etymological Dictionary of the English Language," 1898]

The meaning "put in a certain position" in English is from early 15c. The intransitive sense of "assume a certain attitude or character" (with implications of artificiality) is from 1840; the transitive sense in reference to an artist's model, etc. is from 1850. Related: Posed; posing. 

"act or habit of misapplying words through ambition to use fine language," also a word so misapplied, 1826, from Mrs. Malaprop, character in Sheridan's play "The Rivals" (1775), noted for her ridiculous misuse of large words (such as contagious countries for contiguous countries), her name coined from malapropos.

When Mrs. Malaprop, in Sheridan's Rivals, is said to 'deck her dull chat with hard words which she don't understand,' she protests, 'Sure, if I reprehend anything in this world it is the use of my oracular tongue, & a nice derangement of epitaphs'—having vague memories of apprehend, vernacular, arrangement, & epithets. She is now the matron saint of those who go wordfowling with a blunderbuss. [Fowler]