Earlier quoted context omitted.
I still don't get WETH. What is the purpose of exchanging ETH, which is a token on the Ethereum blockchain, for WETH, which is also a token on the Ethereum blockchain (with the same nominal value)?
After a while a standard api was invented for tokens that use smart contacts on ethereum. ETH predates these standards and is built in to the operation of the blockchain. Lots of smart contacts know how to deal with standard tokens but don't have a separate code path to deal with ETH. You can get a version of ETH that fits the interface by wrapping it in a standard token.
I mean, Java class naming wouldn’t be any better but “WETH” is just extending a base class with an interface.