Impossible to know without asking the creators, but probably chose.

There are dozens of other things called Opus. Just check the Wikipedia page: https://en.wikipedia.org/wiki/Opus

It would be pretty hard to choose that name without becoming aware of at least one of these. The creators most likely just deemed these other uses too obscure and unrelated to matter, which is fair because it's pretty hard to pick a good name that hasn't already been used somewhere.

Perhaps they wanted to be difficult to find using a Google search. Like the ".NET" framework.