puppy (n.)

late 15c., "woman's small pet dog," of uncertain origin but likely from French poupée "doll, toy" (see puppet). Meaning shifted from "toy dog" to "young dog" (1590s), replacing Middle English whelp. In early use in English puppet and puppy were not always distinct from each other. Also used about that time in sense of "vain young man." Puppy-dog is attested by 1590s (in Shakespeare, puppi-dogges). Puppy love is from 1823. Puppy fat is by 1937.