This sounds distinctly risqué, but is in fact (if several Internet sources are to be believed) quite innocent. According to the Australian National University:
"The term derives from the joking notion (as perceived from the southern states of Australia) that Queenslanders spend their time putting bends into bananas. An article from 15 July 1937 in the Queenslander provides a forerunner to the term when a man is asked by the Queen what his occupation is:
"I'm a banana–bender". Further to enlighten her Majesty he explained that bananas grew straight on the trees, and so just before they ripened, [his job was] to mount the ladder, and with a specialised twist of the wrist, put into the fruit the Grecian bend that was half its charm.
"The association of bananas with Queensland ('banana land') is based on the extensive banana–growing industry in tropical Queensland. The Queensland border has been called the Banana curtain and Brisbane has been called Banana city. Banana bender, in reference to a Queenslander, is first recorded in 1940 and is [s]till commonly heard."
And if that story was clean enough for Queen Mary in 1937, it's clean enough for me.
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