Mommy as a slang term

Every time I speak to a Spanish man either in the store or at the McDonalds pay window , I am referred to as "mommy". I know what the word means in english but i'm guessing this is a slang word that spanish men use sometimes when talking to a woman. Please tell me the inferance. Is this a compliment ? Also, I am a transgender woman. Would that have anything to do with it?