Knowing proper names is fine, of course, as long as both sides are on the same page if one player knows it and the other one doesn't, you might still have to resort to crude descriptions.

Buffy Speak: The Keypad module often has defusers resorting to terms like 'smiley face with a tongue out' and 'looks like a caterpillar' to describe unfamiliar symbols.

It also helps if you know that Ur was a city in ancient Sumer.

This can save a lot of time that is usually needed to clarify just which of the same-sounding words they are referring to.

Both the expert and the defuser knowing any second language (as long as it is the same) can be very useful when dealing with the 'Who's On First' module, as homophones can be referred to by their translation in the other language.

The bomb-defuser knowing Morse code can make that module MUCH easier. While it is not required, knowing the language of some of the symbols in the Keypad module (like Cyrillic script or Greek) saves you the trouble of trying to describe weird-looking characters.

Keep talking and nobody explodes