diminutive suffix, first attested late 12c. in proper names adopted from Flanders and Holland. As it is not found in Old English it probably is from Middle Dutch -kin, properly a double-diminutive, from -k + -in. Equivalent to German -chen. Also borrowed in Old French as -quin, where it usually has a bad sense.
This suffix, which is almost barren in French, has been more largely developed in the Picard patois, which uses it for new forms, such as verquin, a shabby little glass (verre); painequin, a bad little loaf (pain); Pierrequin poor little Pierre, &c. ["An Etymological Dictionary of the French Language," transl. G.W. Kitchin, Oxford, 1878]
Used in later Middle English with common nouns. In some words it is directly from Dutch or Flemish.
word-forming element making nouns of quality, state, or condition, from Middle English -our, from Old French -our (Modern French -eur), from Latin -orem (nominative -or), a suffix added to past participle verbal stems. Also in some cases from Latin -atorem (nominative -ator).
In U.S., via Noah Webster, -or is nearly universal (but not in glamour), while in Britain -our is used in most cases (but with many exceptions: author, error, tenor, senator, ancestor, horror etc.). The -our form predominated after c. 1300, but Mencken reports that the first three folios of Shakespeare's plays used both spellings indiscriminately and with equal frequency; only in the Fourth Folio of 1685 does -our become consistent.
A partial revival of -or on the Latin model took place from 16c. (governour began to lose its -u- 16c. and it was gone by 19c.), and also among phonetic spellers in both England and America (John Wesley wrote that -or was "a fashionable impropriety" in England in 1791).
Webster criticized the habit of deleting -u- in -our words in his first speller ("A Grammatical Institute of the English Language," commonly called the Blue-Black Speller) in 1783. His own deletion of the -u- began with the revision of 1804, and was enshrined in the influential "Comprehensive Dictionary of the English Language" (1806), which also established in the U.S. -ic for British -ick and -er for -re, along with many other attempts at reformed spelling which never caught on (such as masheen for machine). His attempt to justify them on the grounds of etymology and the custom of great writers does not hold up.
Fowler notes the British drop the -u- when forming adjectives ending in -orous (humorous) and derivatives in -ation and -ize, in which cases the Latin origin is respected (such as vaporize). When the Americans began to consistently spell it one way, however, the British reflexively hardened their insistence on the other. "The American abolition of -our in such words as honour and favour has probably retarded rather than quickened English progress in the same direction." [Fowler]
often before vowels pseud-, word-forming element meaning "false; feigned; erroneous; in appearance only; resembling," from Greek pseudo-, combining form of pseudēs "false, lying; falsely; deceived," or pseudos "falsehood, untruth, a lie," both from pseudein "to tell a lie; be wrong, break (an oath)," also, in Attic, "to deceive, cheat, be false," but often regardless of intention, a word of uncertain origin. Words in Slavic and Armenian have been compared; by some scholars the Greek word is connected with *psu- "wind" (= "nonsense, idle talk"); Beekes suggests Pre-Greek origin.
Productive in compound formation in ancient Greek (such as pseudodidaskalos "false teacher," pseudokyon "a sham cynic," pseudologia "a false speech," pseudoparthenos "pretended virgin"), it began to be used with native words in later Middle English with a sense of "false, hypocritical" (pseudoclerk "deceitful clerk;" pseudocrist "false apostle;" pseudoprest "heretical priest;" pseudoprophete; pseudofrere) and has been productive since then; the list of words in it in the OED print edition runs to 13 pages. In science, indicating something deceptive in appearance or function.
word-forming element expressing incomplete resemblance (such as poetaster), usually diminutive and deprecatory, from Latin -aster, from a suffix forming nouns from verbs ending in Greek -azein; in later Latin generalized as a pejorative suffix, as in patraster "he who plays the father."