schistosome n.

word-forming element meaning "division; split, cleavage," from Latinized form of Greek skhizo-, combining form ("irregular," says OED) of skhizein "to split, cleave, part, separate" (from PIE root *skei- "to cut, split").

before vowels somat-, word-forming element used in the sciences from mid-19c. and meaning "the body of an organism," from combining form of Greek sōma (genitive sōmatos) "the body, a human body dead or living, body as opposed to spirit; material substance; mass; a person, human being; the whole body or mass of anything," a word of uncertain origin.

According to Watkins perhaps originally "compactness, swelling," and from PIE root *teue- "to swell," but Beekes finds for it "no convincing etymology." In Homer sōma is typically "dead body," as opposed to demas "living body, bodily shape, outward appearance;" in philosophy it is opposed to psykhē "the soul, mind, spirit." The Greek word also was used generally of material substances and physical masses.