rennet (n.1)youdaoicibaDictYouDict[rennet 词源字典]
"inner membrane of a calf's fourth stomach," c. 1400, probably from an unrecorded Old English *rynet, related to gerennan "cause to run together," because it makes milk run or curdle; from Proto-Germanic *rannijanan, causative of *renwanan "to run" (see run (v.)). Compare German rinnen "to run," gerinnen "to curdle."[rennet etymology, rennet origin, 英语词源]