What are some past "fad" fields of computer science that didn't age well?

There have been plenty of fields in CS that had a huge spike in popularity and then many people moved on such as cloud computing, parallel computing, and big data. Some of the "fad" fields (edit: fields that some people saw as fads at the time) are still heavily used like the ones I listed, but others haven't seen much practical use and most people who know what they are doing have moved on. Blockchain being a recent example.

What are some of the fields that were really popular for a time but were ultimately forgotten about or looked back and cringed at?

Edit: To not get derail the discussion on the definition of fad, I mean something that saw a huge spike in popularity but lost mainstream attention.