As an affectionate form of address (to a female): sweetheart, dear.
Origin
1970s; earliest use found in Current Slang. From American Spanish mijita, also (in Central America and the Caribbean) mi'jita, affectionate form of address to a female child or younger woman, shortened from mi hijita (although attested only from 1927 as form of address) from mi my + hijita little daughter, little child.