What does Lou mean?
Lou has 1 masculine form: Louis.
Lou is a very popular first name for females (#604 out of 4276, Top 14%) and also a very popular surname for both adults and children (#11758 out of 150436, Top 8%). (2000 U.S. Census)
Presented below is the birth name popularity of Lou for girls. Lou reached its top rank of #157 in the U.S. then, but is not listed at the moment. (Top 1000 Birth Names Records, 2014)
Prominent alternative forms of Lou are Lucy (#62 last year), Lola (#236), Luanne, Luella, Lulu, Lula, Luann, Luana, Louann, Louella, Louise and Lu. These girl names were at the height of their popularity during 1880-1889 (usage of 0.5432%) and are now significantly less widespread (usage 0.1309%, down 75.9%), with forms like Louann, Louella, Louise, Lou and Luann falling out of style. Lucy (#62) and Lola (#236) are two of the more fashionable baby names in this list, and there is a rebound in birth name usage for Lola and Lucy. Below is a graphed comparison of the usage of the girl name Lou and affiliated names. (Top 1000 Birth Names Records, 2014)