Over the past 110 years, 26 842 girls and 504 boys have been named Lou. The name Lou ranks 759th in the United States among the most common names for girls. For the first time more than ten times newborns were named Lou in 1910. The peak of popularity of the name Lou came in the 1930s and 1950s. You can see absolute numbers and relative numbers on the chart. Indicators per 100K more accurately assess the popularity of the name.