At mainframe shops, where the computers have operators for routine administrivia, the programmers and hardware people tend to look down on the operators and claim that a trained monkey could do their job.
It is frequently observed that the incentives that would be offered said monkeys can be used as a scale to describe the difficulty of a task.
A one-banana problem is simple; hence, "It's only a one-banana job at the most; what's taking them so long?"
At IBM, folklore divides the world into one-, two-, and three-banana problems.
Other cultures have different hierarchies and may divide them more finely; at ICL, for example, five grapes (a bunch) equals a banana.
Their upper limit for the in-house sysape
s is said to be two bananas and three grapes (another source claims it's three bananas and one grape, but observes "However, this is subject to local variations, cosmic rays and ISO").
At a complication level any higher than that, one asks the manufacturers to send someone around to check things.
See also Infinite-Monkey Theorem.