word-forming element in nouns of act, process, function, condition, from Old French and French -age, from Late Latin -aticum "belonging to, related to," originally neuter adjectival suffix, from PIE *-at- (source of Latin -atus, past participle suffix of verbs of the first conjugation) + *-(i)ko-, secondary suffix forming adjectives (see -ic).
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.