make an ass or monkey out of. Cause someone or oneself to look foolish or stupid. For example, John doesn't mind making a fool of himself at parties, or They made an ass of me by giving me the wrong instructions, or Just watch him make a monkey out of this amateur chess player. The use of fool and ass date from the early 1600s; the latter is sometimes put more rudely as make a horse's ass of, alluding to a horse's behind. The use of monkey dates from about 1900.