FiraGO is a typeface that builds on Fira Sans and adds additional
language support.

From bBoxType's website:

Based on the Fira Sans 4.3 glyph set, FiraGO now supports Arabic,
Devanagari, Georgian, Hebrew and Thai. With this script support,
FiraGO catches up with other global Open Source typefaces such as
Noto.

We [bBoxType] decided to introduce FiraGO as a new product. That way,
users of Fira Sans can also install FiraGO.