Brennan is a distinctive girls' name in United States, ranking #2485 in 1997 with 52 recorded births. The name reached its all-time peak in 2007 with 100 births ranking #2039. Since 1996, the popularity has decreased by 13.3%. In 1997, approximately 1 in every 33,474 girls born was named Brennan. FALLING Recent data shows the name is currently falling.