It's intentionally to get across the idea that you don't, and shouldn't, know anything about these arguments within this scope beyond "this is a function" and "this is an argument". These functions just define how to combine things; if you knew any more about the arguments, it would be breaking the abstraction.
The only better names you could really give are ones like func1, func2, arg1, arg2, which don't add any information, just add noise. Trying to get any more specific than that would leave the reader trying to interpret the meaning of the name, but the whole point is that it's strictly "apply this thing to that in this way, without looking at what they are". Even fix-point, which is unarguably cryptic, really needs a paragraph explanation for the unfamiliar more than it would benefit from better names.
The only better names you could really give are ones like func1, func2, arg1, arg2, which don't add any information, just add noise. Trying to get any more specific than that would leave the reader trying to interpret the meaning of the name, but the whole point is that it's strictly "apply this thing to that in this way, without looking at what they are". Even fix-point, which is unarguably cryptic, really needs a paragraph explanation for the unfamiliar more than it would benefit from better names.