Just gonna say, "Gauna" is probably from the moth genus, not the Sanskrit. Nihei seems to have a whole thing about moths going on in many of his works -- like the moth/butterfly lifecycle diagram near the start of Biomega -- and Suzumega and its altered republication Sphingidae bring back the Gauna in a work with a lot of moth-related theme naming... and this even carries into Sidonia with the Benisuzume Gauna. It's not 100%, but it seems like the most plausible.
Speaking of, Suzumega focuses on what seems an awful lot like a battle between an unknown race (possibly strangely-dressed or mutated humans) using seeming normal humans piloting mecha based on the Abara Gauna to fight against something like the Sidonia Gauna, and overall seems like a very early version of Sidonia.
