Brennan is a distinctive girls' name in United States, ranking #2344 in 2010 with 81 recorded births. The name reached its all-time peak in 2007 with 100 births ranking #2039. Since 1996, the popularity has increased by 35.0%. In 2010, approximately 1 in every 21,942 girls born was named Brennan. FALLING Recent data shows the name is currently falling.