Diminutive for many names across Europe ending in -lena, e.g Helena, Magdalena, etc. In Scotland this includes female derivations from male names by the addition of the Scottish suffix -ina, e.g. Dolina [q.v.].
Lena is also widely used as a given name.
A private correspondent notes that in Wales Lena is a pet name for Eluned [q.v.].