Are they? I've mostly seen stuff with 'N' at the beginning, e.g., "NHibernate", "nUnit", "NAnt", "Noda Time", etc.
There's an "IronLanguages" project that does IronPython, IronRuby, etc., but it seems mostly to be concentrating on porting programming languages to the CLR.
Here's a blog post explaining the name. It quotes the creator of the IronPython project:
I'll give you the story, but I'll give you the short version 'cause it's not very good.
At the time, I had a consulting company called "Want of a Nail Software". "Want of a Nail" is based on a children's poem. It's about the importance of small things. I've always kind of believed in the importance of small things. Part of the story of IronPython's actual performance is it wasn't one big thing - Everybody wants to know "What was the one big thing?" There were some big things, but most of it was all the small things - paying attention to performance in every place.
So, that was the consulting company and "Iron" seemed to match.
There were some obvious names: Python.Net, Python#, nPython - All of those were taken. All of the URLs for those were registered.
I didn't want to reuse any of those names, so "Iron" was just kind of a name that appealed to me at a visceral level - I like the feeling of "IronPython".
There's a little bit of "Iron Chef" in it, although I'm always reluctant to admit that.