I remember the first time I found out about this, I mentioned it to a friend and they linked me to the profanity dictionary their company uses. While perusing through the list and having a laugh at some of the words that are filtered, like "cumtart", "dickweasel", "mastrabator", and "wankerers" to name a few I realised that someone must have sat there thinking up some of these words to filter them. That must have been a fun afternoon.
I was that someone at a company in the early 2000s. I can confirm that it was, in fact, fun.
A coworker and I came up with every offensive word we could think of over a few days. Then, on Friday afternoon, we shared a 6 pack and got really inventive.
I'd imagine the list is still kicking around that company somewhere and hope it is our eternal legacy.
A friend pointed out to me that Microsoft Word wouldn't underline swear words (because they are spelled correctly), but also wouldn't suggest if they were misspelled.
I spent many a happy afternoon in Word VBA (it was a while ago) trying to get access to the list that it must keep!
I used to moderate reddit and we had a slur filter. It had the stuff you'd expect, but so much you wouldn't. Like why are people being so creatively anti Italian in the 21st century shit. I'd occasionally have to add something new to the automod list because bigots have nothing better to do