In Danish, it's "snabel-a", ie "[elephant's] trunk-a". # was at a time when a popular youth radio show had an IRC channel called "havelåge" or "garden gate", but "firkant" (simply "square") was and remains in wide use in voice response systems. Neither symbol had as far as I know any mainstream use before this time.
# in internet-contexts has transitioned to "hashtag" (remains "firkant" in voice response), but as far as I know snabel-a is still in use (I just realised that I haven't participated in a Danish verbal transmission of an email address in quite a while).
In Bulgaria it's gone through several disjointed phases. You can use either "кльомба" (klyomba, I have no idea what it's supposed to mean), "маймунка" (maymunka, monkey), "маймунско А" (maymunsko A, monkey A) or "at" to refer to it.
In Swedish you can hear "snabel-A" (trunk-A, same as in Danish) or "at".
In Finland we call it "kissanhäntä" (cat's tail) or "miukumauku". "Miu" and "mau" are actually cat's meows, so "miukumauku" is kind of a "a meow, a meow" with two different words.
Nowadays it's usually called "ät-merkki" as in "at-sign" as "at" is spelled in Finnish.
I was just going to say the same for Russian, but you beat me to it. Never really thought about why we have named it that way though, it was always something I just accepted... seems weird now.
The circle bit looks like a monkey tail, simple as that. And there was no need for a shorter word, as it really wasn't used in common speech or writing (the French "à" was/is used in the commercial sense).
My guess used to be that it started as a "Klammer-A" ("a in a bracket") and that at some point the joking extension from A to Affe (monkey or ape, everyday German does not make a distinction) went viral, supported by the tail-like shape. Now that I know that the monkey connection even exists in languages without the a -> Affe link I'm not so confident anymore.
I can only speculate but I believe it is due to the fact that it kind of looks like a paper clip shaped like a monkey ear (speculation on my part but I've heard that before).
Klammer is short for Büroklammer (= paper clip) and Affe is monkey (or ape).
# in internet-contexts has transitioned to "hashtag" (remains "firkant" in voice response), but as far as I know snabel-a is still in use (I just realised that I haven't participated in a Danish verbal transmission of an email address in quite a while).