It looks very much like it's a
German pet name, a la
Gretchen,
Madchen,
Jochen etc.
A best guess would be that it's a pet form of
Lena, but there's a few other names it could be a pet name for.
Does a
German origin make sense in the context of the book?
♦ Chrisell ♦
All we have to decide is what to do with the time that is given us. - J.R.R. Tolkien.