1560s, general term of endearment (also puggy), probably related to puck, n.2; one of the earliest senses is "sprite, imp" (1610s). The sense of "miniature dog" is from 1749 (pug-dog); that of "monkey" is 1660s. The word at various times meant "a bargeman" (1590s), "a harlot" (c.1600), and "an upper servant in a great house" (1847).