word forming element indicating "oneself," also "automatic," from Old English use of self (pron.) in compounds, such as selfbana "suicide," selflice "self-love, pride, vanity, egotism," selfwill "free will." Middle English had self-witte "one's own knowledge and intelligence" (early 15c.).
OED counts 13 such compounds in Old English. Middle English Compendium lists four, counting the self-will group as a whole. It re-emerges as a living word-forming element mid-16c., "probably to a great extent by imitation or reminiscence of Greek compounds in (auto-)," and formed a great many words in the pamphlet disputes of the 17c.
c. 1500, "address with a title;" 1560s, "to give a name to," from style (n.). Meaning "to arrange in (fashionable) style" (especially of hair) is attested from 1934. Slang sense of "act or play in a showy way" is by 1974, African-American vernacular. Related: Styled; styling.
<a href="https://www.etymonline.com/word/self-styled">Etymology of self-styled by etymonline</a>
Harper, D. (n.d.). Etymology of self-styled. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/self-styled