Modern variation of Hennessy, meaning descendant of Angus
Jennessy is a modern American invention, likely created by blending the popular 'Jen-' prefix with the surname-turned-given-name Hennessy. The root name Hennessy is an Anglicized form of the Irish Γ hAonghusa, which denotes a descendant of Aonghus (Angus), a name traditionally interpreted as 'one strength'.
Less common today
Jennessy isn't in the latest US Top 1000. It last peaked at #9,267 in 2009.
US births per 5-year period, 1990βpresent (SSA data).