late 13c. distourben, "to frighten, alarm, break up the tranquility of;" c. 1300, "to stop or hinder;" from Old French destorber (Old North French distourber) and directly from Latin disturbare "throw into disorder," from dis- "completely" (see dis-) + turbare "to disorder, disturb," from turba "turmoil" (see turbid). Related: Disturbed; disturbing; disturbingly.
Middle English also had the verb as distourblen, from Old French destorbler; hence also distourbler (n.) "one who disturbs or incites" (late 14c.).
also sangfroid, "presence of mind, coolness, mental composure," 1712, from French sang froid, literally "cool blood," from sang "blood" (from Latin sanguis; see sanguinary) + froid "cold" (from Latin frigidus; see frigid). "In the 17th c. the expression was in France often written erroneously sens froid, as if it contained sens "sense" instead of the homophonous sang "blood'." [OED].