Maths, but if we don’t count that - Latin. It gives me a second level of understanding of words in English. There’s the English meaning of say concatenation of events. I look at it and think simultaneously the literal meaning of con catena in Latin - “with chain”, and then past participle of evenire, with the ending dropped off.
I read a lot of law and medical research - both use Latin words quite a bit, so I can understand the jargon literally.