Hennessy is a distinctive boys' name in United States, ranking #12781 in 2015 with 5 recorded births. The name reached its all-time peak in 1996 with 7 births ranking #7432. Since 1996, the popularity has decreased by 28.6%. In 2015, approximately 1 in every 383,252 boys born was named Hennessy. STABLE Recent data shows the name is currently stable.