Answer:
Well. back in the Prohibition days in the early 1910-1920's. In California, there was this lady who sold alcohol but she had to stop. Her name was Aunt Jane (Tia Juana in spanish). So she crossed the border (white girl) and sold right on the frontier..Every American used to say, "Let's go see AUnt Jane, she's got liquor. Hence The name stuck in the area. Tia Juana....Tijuana