Hennessy is a distinctive and unique given name of Irish origin, derived from the Irish surname Ó hEanachaidh, which means 'descendant of Eanachadh.' It translates to 'from the riverside,' as it signifies someone who lived near a riverbank or by a river. The name Hennessy gained prominence during the 18th century, with notable figures such as James Hennessy, an Irish politician and lawyer, contributing to its recognition.
The name Hennessy experienced a consistent popularity throughout the late 90s and early 2000s with at least 7 births per year from 1996 to 1998. There was a dip in popularity between 1999 and 2001, but it picked up again in 2007. After another decrease between 2007 and 2015, the name's popularity rebounded with 6 births each in 2016 and 2018. Overall, there have been a total of 56 babies named Hennessy born since 1996.