Source : Webster's Revised Unabridged Dictionary (1913)

Requin \Re"quin\ (r?"kw?n), n. [F., fr. reqiem a Mass sung for
   the dead. See {Requiem}.] (Zo["o]l.)
   The man-eater, or white shark ({Carcharodon carcharias}); --
   so called on account of its causing requiems to be sung.