

It was first found in monkeys, but actually originated in rodents. It should technically be rodentpox.
Also, racists and homophobes used it to create stigma against gay men. In was/is particularly prevalent in that group. There were rumours that you caught it from sex with monkeys.
Basically it was renamed to pull the teeth of a nasty and insulting use, and to break a misunderstanding on its source.
Things like this are often a protest by the builders against the architect. They spot a problem with the design, try and tell them and get shouted at. They then build it to the design, knowing it’s stupid, so the architect has to swallow the cost of fixing it.