Nomen oblitum

So, imagine you have a friend called Tom. He's your friend for a long time and you call him Tom all the time. But one day, you talked to your other friends and found out that his real name is actually Tim. You didn't know that before and you're surprised!

Nomen oblitum is like that, but with words. It means "forgotten name" in Latin. Sometimes people use a word for a long time, but they don't know what it really means or where it comes from. Later, someone discovers the real meaning or origin of the word, and it turns out that the old word isn't right anymore.

Like if people used to call the Sun "Helios," but then they discovered that it's actually a star and not a god driving a sun chariot. So now they call it "Sun" instead of "Helios." Helios is a nomen obitum because it's no longer used and forgotten.

In summary, nomen oblitum is when people used a word for a long time, but then they found out that it's not the right word anymore. So the word is forgotten or replaced with a better one.