Brennan is a moderately popular boys' name in United States, ranking #299 in 2006 with 1,116 recorded births. The name reached its all-time peak in 2009 with 1,464 births ranking #242. Since 1996, the popularity has increased by 24.7%. In 2006, approximately 1 in every 1,842 boys born was named Brennan. STABLE Recent data shows the name is currently stable.