rennet

Etymology 1

From Middle English renet, a variant of renelesse, renels, renlys, rendlys (“rennet”), from rennen (“to run”), from Old English rennan, from Proto-Germanic *rannijaną. Compare Middle Dutch rinsel, runsel (“rennet”), Middle English irennen (“to curdle; to run”), Old English ġerennan (“to coagulate”), German gerinnen (“to coagulate; congeal”).

noun

1. An enzyme used as the first step in making cheese, to curdle the milk and coagulate the casein in it, derived by soaking the fourth stomach of a milk-fed calf in brine.

Etymology 2

Anglicized form of reinette.

noun

1. Alternative form of reinette.
   The choice of treats is between a sweet mandarin orange and maybe a lumpy rennet apple. Nothing is packaged; there is only food here in this market, most of it requiring washing and chopping and cooking. 2014, Jeannie Marshall, The Lost Art of Feeding Kids: What Italy Taught Me about Why Children Need Real Food, Beacon Press, page ?