Hennessey is a distinctive girls' name in United States, ranking #9963 in 2012 with 11 recorded births. The name reached its all-time peak in 2015 with 27 births ranking #5037. Since 1996, the popularity has increased by 83.3%. In 2012, approximately 1 in every 160,067 girls born was named Hennessey. FALLING Recent data shows the name is currently falling.