sigmoid (adj.)

18th letter of the Greek alphabet, corresponding to Latin S; the name is a metathesis of Hebrew samekh. In uncial writing, shaped like an S or a C.

word-forming element meaning "like, like that of, thing like a ______," from Latinized form of Greek -oeidēs (three syllables), from eidos "form," related to idein "to see," eidenai "to know;" literally "to see" (from PIE *weid-es-, from root *weid- "to see"). The -o- is connective or a stem vowel from the previous element. Often implying an incomplete or imperfect resemblance to the thing indicated.

"speculum for examining the lower bowels," 1895, from sigmoid (q.v.) in the colonic sense + -scope, with connective -o-. Related: Sigmoidoscopy.