Hanuman asana refers to the position in which lord Hanumana in the epic scripture Ramayana, jumbed taking a huge leap over the ocean to Sri Lanka, to take such a big jump Hanumana took a leg forward and back leg was straight backword, also known as front split.
Source: https://www.vinyasayogaashram.com/blog/hanumanasana-how-to-do-it-benefits-and-precautions/