In German they are called “Zitteraal” literally translated: tremble eel
Named after the people who were trembling on touch.
I was curious and started reading into it, apparently the ancient Egyptians used to call electric fish (as they hadn’t discovered electric eels by that point) “Thunderer of the Nile”
Spicy waternoodles
They were called nothing (at least in English) because they were first described somewhere in the 18th century and they knew about electricity by then. Boring answer, but that’s how it is.
Yep. Nothing existed before the 18th century white explorer came along and named everything in English.
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.