From what I understand, they’re named in the order they were released and based on Gaston Glock’s patent timeline. For example, the G17 came first (he had other polymer non-gun stuff beforehand), then the compact G19, then the baby G26 and…much later… The ultra-compact G43. Other stuff came in between those model numbers.
Really? I’ll have to check that out because I thought it was that way for a long, long time. Look at me providing BS info. LOL