An Etymological Dictionary of Astronomy and Astrophysics

A prefix occurring in loanwords from Gk., having the same function as → co-; used, with the meaning “with, together,” in the formation of compound words. Variants sy-, syl-, sym-, sys-.

Etymology (EN): From Gk. syn “with, together with,” of unknown origin.

Etymology (PE): Ham- “together, with; same, equally, even,” Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- “one and the same,” Skt. sama-, Gk. homos-;
originally identical with PIE numeral *sam- “one,” from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-.