San is the apocope of santo (masculine form of saint), all masculine names use the form San except those that start with the syllables to- or do-.

Yeah, "Santo" is the better example. I'm actually not sure if there's any particular distinction for why sme place names are "San" and other are "Santo", perhaps it comes from historical baggage from whichever branches of explorers / conquerers founded each town.

My understanding is we have the Dutch to blame for that as they named him "Sante" and Spanish-speaking countries adapted the sound into "a" for whatever reason. Basically it's "whole" proper name derived from elsewhere.

He's a world-famous forklift driver.

Well, Santa Claus doesn't operate in Spain so they got confused somewhere when translating the name