Brennan is a moderately popular boys' name in United States, ranking #276 in 2003 with 1,127 recorded births. The name reached its all-time peak in 2009 with 1,464 births ranking #242. Since 1996, the popularity has increased by 25.9%. In 2003, approximately 1 in every 1,753 boys born was named Brennan. STABLE Recent data shows the name is currently stable.