Brennan is a distinctive girls' name in United States, ranking #2609 in 2006 with 69 recorded births. The name reached its all-time peak in 2007 with 100 births ranking #2039. Since 1996, the popularity has increased by 15.0%. In 2006, approximately 1 in every 27,552 girls born was named Brennan. FALLING Recent data shows the name is currently falling.