From the Spanish root word "chancla," which means "flip flop" (like the cheap shoes). A "chancluda", literally meaning "A female wearing flip flops," but in Mexico, prostitutes pride themselves on their shoes, and a prostitute wearing flip flops is the cheapest, skankiest, sluttiest, nastiest hooker out there because she charges so little (because of her disgusting appearance) that she can only afford to buy flip flops with her meager earnings. Hence, a "chancluda" is a whore of the very lowest standards in Mexico.
One might use the verbiage of: "Your mother is a skanky ass chancluda, bitch." when attempting to insult a spanish-speaking rival.