The name reached its all-time peak in 2015 with 9 births ranking #11303. FALLING Recent data shows the name is currently falling.
Jaxx is a spelling variant of Jax, so it ultimately follows the same route back to Jackson. It is mainly a style-driven modern spelling rather than a separate traditional name.
This version reflects the modern taste for bold alternative spellings. Behind the Name treats it directly as a variant of Jax rather than giving it a separate older origin story.