Hennessey is a distinctive girls' name in United States, ranking #8574 in 1997 with 10 recorded births. The name reached its all-time peak in 2015 with 27 births ranking #5037. Since 1996, the popularity has increased by 66.7%. In 1997, approximately 1 in every 174,066 girls born was named Hennessey. FALLING Recent data shows the name is currently falling.