Gear inches (GI) is a concept that goes back to the early says of bicycles, the high wheelers. A "gear inch" is how far a high wheeler would go with a 1" diameter front wheel. (Yeah, ridiculous but a kiddie on his tricycle has a 16" GI.) Racers (mankind will always race the next contraption that comes along) quickly figured out the bigger that front wheel, the faster the bike, limited only by the length of legs of the rider. (Their seats always looked to high, for very good reason.) When the chain bicycle came along and therefore gear ratios, they just naturally spoke of this new geared setup as being equivalent to the old front wheel, using the same (equivalent) diameter n inches.
So your 101" gear is the equivalent of a 101" high wheeler (to be ridden by the NBA's tallest).
Yes, an archaic way of expressing gear ratios. But it does describe the gears we use with simple 2 digits (3 for the really big ones). 20 to 120 covers most of what we ride. No decimals needed. Also has the nice feature that it takes wheel size into account, making comparisons between (say) a standard 27"/700c bike and a small wheeled folder easy.