cast-
(Latin: pure, cut off, to cut off from, separated)
A reference to "a race of men" is from Latin casto, "chaste" from castus, "pure, cut off, separated"; past participle of carere, "to be cut off from" (and related to castrate and -cest-).
Related cutting-word units: castrat-; -cise, -cide; -ectomy; mutil-; put-; sec-, seg-; temno-; -tomy; trunc-.