"self-named, so-called, would-be," 1752 (in Chesterfield), French, from soi "oneself" (from Latin se, see se-) + present participle of dire "to say" (from Latin dicere "speak, tell, say," from PIE root *deik- "to show," also "pronounce solemnly").
word-forming element, from Latin se-, collateral form of sed- "without, apart, aside, on one's own," related to sed, Latin reflexive pronoun (accusative and ablative), from PIE *sed-, extended form of root *s(w)e-, pronoun of the third person and reflexive (source also of German sich; see idiom).
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dic- "point out, show;" Greek deiknynai "to show, to prove," dike "custom, usage;" Latin dicere "speak, tell, say," digitus "finger," Old High German zeigon, German zeigen "to show," Old English teon "to accuse," tæcan "to teach."
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Definitions of soi-disant
as claimed by and for yourself often without justification;