Disambiguation. There is one thing called protobufs. There are hundreds called "ion", a lot of which are more notable than an internal file format.

Edit: I was going to paste in a relevant quote from Zarf (i.e. Andrew Plotkin) on naming. Some of his most important programs have total nonsense names like "glulx", and the reasoning was that at least it would be easy to search for when the name is unique. But ironically, "Zarf" is so common a term that I can't find the quote.