The Marines in China before WW II were issued candy (Baby Ruths, Tootsie Rolls, etc.) as part of their their ration supplements. At the time, sugar and other assorted sweets were rare commodities in China and much in demand by the Chinese, so
the troops found the candy useful for barter in town.
The Chinese word for
prostitute, roughly
translated, is "pogey". Thus, Marines being Marines, candy became "Pogey Bait".