Brennan is a moderately popular boys' name in United States, ranking #286 in 2007 with 1,207 recorded births. The name reached its all-time peak in 2009 with 1,464 births ranking #242. Since 1996, the popularity has increased by 34.9%. In 2007, approximately 1 in every 1,719 boys born was named Brennan. STABLE Recent data shows the name is currently stable.