sang-froid n.

1620s, "characterized by slaughter, attended by much bloodshed;" also bloodthirsty, eager to shed blood, delighting in carnage," from French sanguinaire or directly from Latin sanguinarius "of or pertaining to blood," also, rarely, "blood-thirsty," from sanguis (genitive sanguinis) "blood," a word of unknown origin. Latin distinguished sanguis, the generic word, from cruor "blood from a wound" (related to English raw, from PIE root *kreue-). The classical sense of "pertaining to blood" is rare in English.

1620s, "intensely cold," from Latin frigidus "cold, chill, cool," figuratively "indifferent," also "flat, dull, trivial," from stem of frigere "be cold;" related to noun frigus "cold, coldness, frost," from Proto-Italic *srigos-, from PIE root *srig- "cold" (source also of Greek rhigos "cold, frost"). The meaning "wanting in sexual heat" is attested from 1650s, originally of males. Related: Frigidly; frigidness.