Brennan is a moderately popular boys' name in United States, ranking #270 in 1999 with 1,106 recorded births. The name reached its all-time peak in 2009 with 1,464 births ranking #242. Since 1996, the popularity has increased by 23.6%. In 1999, approximately 1 in every 1,736 boys born was named Brennan. STABLE Recent data shows the name is currently stable.