These days always appears in the plural form and the current meaning for a jackanapes is a mischievous, impertinent person. It dates in this sense from the mid-1500s. The word is derived from the phrase Jack ape, which was a generic name for a male monkey or ape, and which dates from the mid-1400s, Jack being a common name for a male of any description. Apes and monkeys were curious novelties in those days and were popular with the aristocracy and public taverns as pets. Apes and monkeys have a reputation for being mischievous, hence the word’s current meaning.