"inner membrane in the stomach of an unweaned calf or other animal," used for making cheese, etc.; also the mass of curdled milk found in the stomach, mid-15c., 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" (from PIE root *rei- "to run, flow"). Compare German rinnen "to run," gerinnen "to curdle." Hence, "anything used to curdle milk."
variety of apple, mid-15c., renette, from Old French rainette, diminutive of raine, reine "frog," from Latin rana "frog," which probably is imitative of croaking (compare frog (n.1)). If so, so called for its speckled skin like a frog's. The other possibility is that the Old French name of the apple is literally "little queen," a diminutive of reine "queen," from Latin regina (see Regina). OED, which leans toward this suggestion, suggests the other is folk etymology.