Brennan is a distinctive girls' name in United States, ranking #4175 in 2016 with 35 recorded births. This places Brennan in the top 22% of ranked US girls' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 2007 with 100 births ranking #2039. Since 1996, the popularity has decreased by 41.7%. In 2016, approximately 1 in every 50,614 girls born was named Brennan. FALLING Recent data shows the name is currently falling.