"speculum for examining the lower bowels," 1895, from sigmoid (q.v.) in the colonic sense + -scope, with connective -o-. Related: Sigmoidoscopy.
Entries linking to sigmoidoscope
sigmoid adj.
"shaped like the Greek letter sigma" in one of its forms, hence either "shaped like a C" (1660s) or "shaped like an S" (1786). From sigma (q.v.) + -oid. Especially of the flexure of the colon (1891). Related: Sigmoidal; sigmoidally.
-scope
word-forming element indicating "an instrument for seeing," from Late Latin -scopium, from Greek -skopion, from skopein "to look at, examine" (from PIE root *spek- "to observe").