IronPython came first and the rest followed. As for why IronPython is called IronPython, Jim Hugunin goes into that in this video (at about 14:00). He says it was partly to avoid calling it Language.NET or Language#, and the idea is that Iron languages are:
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True language implementations
- True to the language
- True to the community
- True to the experience
- Excellent performance
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Great integration with .NET
- Easy to use .NET libraries
- Easy to use other .NET languages
- Easy to use in .NET hosts
- Easy to use with .NET tools
And a slightly specious acronym explanation, which came after the name:
Implementation Running On .NET.