Chapa is the Spanish version of "shawty" it pretty much means the same thing. Its "chaparrita" but shortened which in Spanish means short girl, kinda like a nickname for ur daughter or loved one. Chapa is a name for ur bottom bitch or even a sexy broad walking down the street. This term is commonly used among the Mexican-Americans, Whitexican-Americans, Blackxican-Americans and others that live around the brown people in the west and south side of Phoenix.
bottom bitch: ayee cariño, what you want me to cook up before you come from work today?
pimpin: damn chapa, you, some strawberry's and some whipped cream sounds good to me.
bottom bitch: ay papi, you sure know how to get a bitch wet.