Thanks to you all for help... and no offense taken, Mänwe, this just happens
I have one last addition to it. I really
don't have Standelf in my version of LotR. One thing I have to point out is, however, that it is not original LotR, but translation to my language (Czech). Nevertheless, I think the translation is quite good - the translator really did a good job and mostly she cared about the smallest details. But since you mentioned that the name "Standelf" is not well seen even on the original map, I find it very likely that Standelf (if it were in the original LotR always) was accidentaly missed by the translator and didn't made it to the map (which is original, just with Czech names).
And one thing, why I always thought Standelf having something to do with "elf" is because the one who translated Fonstad's Atlas named it, in Czech, Elfín (you can see the word "elf" in there, I bet, you would translate it back something like "Elfville" or something like that). I find it likely that the translator didn't bother, or even did not think about Old English roots of this word, just saw "elf" in the word and considered it to mean, well, Elf
So thanks for getting this myth away from me.
It would be harder, however, to get this myth away from many other people, who see just "Elfín" on the map and do not try to look further... guess it's up to me then
Once again a Silmaril to you all for helping to solve this out!