unlike (adj.)

prefix of negation, Old English un-, from Proto-Germanic *un- (source also of Old Saxon, Old Frisian, Old High German, German un-, Gothic un-, Dutch on-), from PIE *n- (source of Sanskrit a-, an- "not," Greek a-, an-, Old Irish an-, Latin in-), combining form of PIE root *ne- "not." Often euphemistic (such as untruth for "lie").

The most prolific of English prefixes, freely and widely used in Old English, where it forms more than 1,000 compounds. It underwent a mass extinction in early Middle English, but emerged with renewed vigor 16c. to form compounds with native and imported words. It disputes with Latin-derived cognate in- (1) the right to form the negation of certain words (indigestable/undigestable, etc.), and though both might be deployed in cooperation to indicate shades of meaning (unfamous/infamous), typically they are not.

It also makes words from phrases (such as uncalled-for, c. 1600; undreamed-of, 1630s; uncome-at-able, 1690s; unputdownable, 1947, of a book; un-in-one-breath-utterable, Ben Jonson; etc., but the habit is not restricted to un-; such as put-up-able-with, 1812). As a prefix in telegramese to replace not and save the cost of a word, it is attested by 1936.

"having the same characteristics or qualities" (as another), c. 1200, lik, shortening of y-lik, from Old English gelic "like, similar," from Proto-Germanic *(ga)leika- "having the same form," literally "with a corresponding body" (source also of Old Saxon gilik, Dutch gelijk, German gleich, Gothic galeiks "equally, like").

This is a compound of *ga- "with, together" + the Germanic root *lik- "body, form; like, same" (source also of Old English lic "body, corpse;" see lich). Etymologically analogous to Latin conform. The modern form (rather than *lich) may be from a northern descendant of the Old English word's Norse cognate, glikr.

Formerly with comparative liker and superlative likest (still in use 17c.). The preposition (c. 1200) and the adverb (c. 1300) both are from the adjective. As a conjunction, first attested early 16c., short for like as, like unto. Colloquial like to "almost, nearly" ("I like to died laughing") is 17c., short for was like to/had like to "come near to, was likely." To feel like "want to, be in the mood for" is 1863, originally American English. Proverbial pattern as in like father, like son is recorded from 1540s.

Meaning "such as" ("A Town Like Alice") attested from 1886. The word has been used as a postponed filler ("going really fast, like") from 1778; as a presumed emphatic ("going, like, really fast") from 1950, originally in counterculture slang and bop talk. Phrase more like it "closer to what is desired" is from 1888.