How do vehicles get their names?

F150 - I'm sure the F stands for Ford, but where did the 150 come from?

Ram 2500 - Why 2500?

S10 - Where does the S come from and the 10?

Arbitrary series numbers.

Auto manufacturers actually have committees that sit around thinking up names for new vehicles. And they do come up with some weird ones! As far as the designation 2500 - several manufacturers do that with their trucks to designate hauling capacity. A Ford F150 is a half-ton pickup. The F250, or in the case of the Ram, it designates a 3/4 ton pickup. Then there's the F350 or the 3500, indicating a one ton truck. Most manufacturers follow that style.

Did you try and google it? https://blog.1aauto.com/2010/12/20/chevy-truck-names-what-the-heck-do-they-mean/

Ram 2500? Because it is heavier duty than a 1500 and not as heavy duty as a 3500. GM/Dodge started out with 10 to 30 on the pickups. Ford was 100. GM/Dodge obviously were better than Ford, so at some point they went to the *500 sizes. The S10 is a small pickup, smaller than the C/K 10.