requiem

Etymology 1

From Middle English requiem, from Latin requiem, the first word of the introit for the traditional requiem mass, an alternative accusative case of Latin requiēs (“rest, repose”), from re- (“again”) + quiēs (“rest, quiet”).

noun

1. A mass (especially Catholic) to honor and remember a dead person.
2. A musical composition for such a mass.
3. A piece of music composed to honor a dead person.
4. (obsolete) Rest; peace.

Etymology 2

From French requin, altered by association with Etymology 1, above.

noun

1. A large or dangerous shark, specifically, (zoology) a member of the family Carcharhinidae.
   Any man-eater is called a requiem. 1973, Patrick Buchanan, A Requiem of Sharks