[Wowfunhappy]

Well, but in this case they're just homonyms, like how the word "bank" can refer to the edge of a river or a financial institution. The gas in your car is short for "gasoline"; you wouldn't call oxygen a type of gasoline, it's a gas.

[a1369209993]

Actually, "bank" isn't just homonyms; both senses derive from circa-Proto-Germanic benc/bank: a bench or other raised area (either a bank counter or the raised ground adjacent to a riverbed). (And yes, this etymology is also shared with "bench".)

[lallysingh]

I think the original financial institutions were actually on the rivers to handle the business around river-transported cargo.