Desuetude

Desuetude is when something is not used for a very long time, and people kind of forget about it. Like if you have a toy that you used to play with all the time, but then you stopped playing with it for so long that you forgot about it, and it just sat in the back of the toy box collecting dust.

Desuetude can happen to things like old laws or customs that people used to follow a long time ago, but then they stopped following them for so long that they kind of forgot they were even there. Over time, these laws or customs can become obsolete and no longer useful, so people might stop caring about them altogether. But sometimes they can also come back into use again, if people suddenly remember about them and start following them again.

Overall, desuetude is just a fancy word for something that used to be important but has been forgotten about because nobody uses it anymore.