köken: Most likely a loanword. Its source is unclear; compare Middle Chinese 侹 (MC thengH) "long, level, straight (obsolete)" → SV: thính. See also bằng. The native Vietic word for "straight" is ngay, which also has Khmuic cognates. It is a semantic loan from English straight, in the sense of “heterosexual”.
köken: Etymology tree Latin sineder. Esperanto sen Esperanto sen- Esperanto ĉesi Esperanto -e Esperanto senĉese From sen- (“without, -less”) + ĉesi (“to cease, stop”) + -e (adverbial ending).
Etimoloji
Attested since circa 1750. Probably from a + a descendant from Proto-Germanic *rēdaz (“advice, counsel”). Compare Catalan arreu, idem.