ape [OE] Until *monkey came into the language in the 16th century, the Old English word ape applied also to monkeys. The verb use ‘to imitate unthinkingly’ was formed when ‘ape’ still meant ‘monkey’, and was suggested by the way that monkeys sometimes mimic human actions. The expression go ape is often thought to be a reference to the 1933 film King Kong, in which a giant ape-like monster goes on the rampage through New York, but the phrase is not recorded until quite a bit later: US newspaper reports from the 1950s say that ‘go ape’ is current teen slang, although others describe it as forces slang. The cruder version go ape shit is recorded from the same time.