"strange person," 1955, from weird. Compare earlier Scottish weirdie "young man with long hair and a beard" (1894).
Entries linking to weirdo
weird adj.
c. 1400, "having power to control fate," from wierd (n.), from Old English wyrd "fate, chance, fortune; destiny; the Fates," literally "that which comes," from Proto-Germanic *wurthiz (source also of Old Saxon wurd, Old High German wurt "fate," Old Norse urðr "fate, one of the three Norns"), from PIE *wert- "to turn, to wind," (source also of German werden, Old English weorðan "to become"), from root *wer- (2) "to turn, bend." For the sense development from "turning" to "becoming," compare phrase turn into "become."
The sense of "uncanny, supernatural" developed from Middle English use of weird sisters for the three Fates or Norns (in Germanic mythology), the goddesses who controlled human destiny. They were portrayed as odd or frightening in appearance, as in "Macbeth" (and especially in 18th and 19th century productions of it), which led to the adjectival meaning "odd-looking, uncanny" (1815); "odd, strange, disturbingly different" (1820). Also see Macbeth. Related: Weirdly; weirdness.
sicko n.
1977, from sick (adj.) in the mental sense + ending as in weirdo. Sickie "perverted person" is attested from 1972; sicknik (1959) "pervert, obscene comedian" (applied to, among others, Lenny Bruce) has the then-faddish -nik ending.