Brennan is a moderately popular boys' name in United States, ranking #274 in 2001 with 1,121 recorded births. The name reached its all-time peak in 2009 with 1,464 births ranking #242. Since 1996, the popularity has increased by 25.3%. In 2001, approximately 1 in every 1,733 boys born was named Brennan. STABLE Recent data shows the name is currently stable.