In the eighteenth century, poker cards were called broads because they were wider than those used for other card games.
Around 1912, because they resembled poker cards, tickets of admission, meal tickets, and transit tickets were being called “broads.”
By 1914, because they were a different kind of “meal ticket,” pimps began calling their prostitutes “broads.”
Soon the term entered the underworld and was eventually picked up by entertainers.
I was told by a real New Yorker I once worked with that Broad meant broad butt. Only women,he said,have big rear ends.In speakeasys they could identify a woman in a mans suite be her larger big backside. Broads alone had no place in the prohibition cafes where drink was sold under the counter. Some woman used to dress in mans attire to gain entrance and so being better shapes than your regular guy she filled out the pants better too.He had it that that was why they are called broads not anything to do with card games.
I also believed broad referred to the hips.