I've never heard the term used and the keyword tool shows it at essentially 0 searches per month (10 to be exact, with some months of 0 searches).
What you have got going for you is that the domain is only 7 letters long, and contains one common word ("last").
Smaller is better.
I think this domain is worth $15. Don't renew it, unless the dumb-dumb college kids make a household name out of "sem" before you have to decide.