Given that the question at hand is limited to the English language, the answer is limited to the English language.

Any names the animal had in other languages will most likely not have changed after electricity was discovered so there will be no change in name there. The joke won't work in most other languages, even if they only discovered out little zappy friends after English speaking people did. In German, the eel is called Zitteraal (twitch-eel), so no need to know what electricity is: "my hand goes twitchy once I touch this slimy sea snake" is enough.