Meaning

noun a person whose behavior deviates from what is acceptable especially in sexual behavior

adjective markedly different from an accepted norm

originFrom Middle English devyaunt (“deviating, different”), from Late Latin dēviāns, present participle of dēviō (“to stray, deviate or detour”). The noun is from the adjective, possibly attested in Middle English with the meaning “one who goes astray”. * (DeviantArt member): So called because the website was originally for people who modified (deviated) computer applications.

Etymology from Wiktionary, CC BY-SA 3.0