/ dʒɒn; NAmE dʒɑːn/ noun
( informal , especially NAmE ) a toilet
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WORD ORIGIN
early 20th cent. (meaning a prostitute's client): from the given name John , used from late Middle English as a form of address to a man, or to denote various occupations, including that of priest (late Middle English ) and policeman (mid 17th cent.).