Nothing certain, but two possibilities to consider re Jelem i. a variant of jelen, "deer", which is Czech, Polish, and doubtless other Slavic languages. Could the end have been changed in some dialect form? I have to say I don't feel confident about this. ii. there is a Czech place name, Jelm, which is very like Jelem. There's also the Czech word jilm, meaning "elm". Jelemensky has to be Slavic, and is likely to be from a place name, but I haven't found it.