Python isn’t only for rank newbies 
. “isqrt” has been in very widespread use for many years in software, dating back at least to Macsyma (late 1960s).
So it would be a disservice to its primary audience to name it something else. Anyway, that ship already sailed.
The same audience won’t be confused by “imath” either. Imaginary numbers on their own aren’t much of “a thing” - they’re subsumed by complex numbers, and cmath is their natural home.
As someone with substantial numeric experience, my first thought at seeing intmath is that it’s probably a collection of functions for doing numerical integration, which is a deep pit all on its own.
“First impressions” vary widely by audience, and I don’t much care about them. What I do care about a lot is whether something is easy to remember and hard to forget after the initial learning curve has been climbed.
Although, admittedly, the learning curve in this case is trivially shallow for imath or intmath. Which do people prefer?
intmathimath- something else
[EDIT] A meta-comment about DIscourse polls. It’s well known that people are biased toward voting for the top-listed candidate in any election. That’s why the voting software the PSF uses randomizes candidate order on ballots, per voter, in PSF elections. So I tried to counter my own mild preference for imath by listing intmath first when I created the poll. But Discourse appears to dynamically reorder the choices from most-votes-so-far to least. That leaves imath at the top now, as I type.