From the OED:
Halfling: Sc. and north, also haflin, hawflin, halflin
A. sb. 1. One not fully grown, a stripling
2. the half of a silverling or old silver penny
B. adj. Not fully grown, about the age of 15
with quotes from 1794 and 1815
however, there is also an entry for Halfling (adv.), Now only Sc.
halflunge, halvelings, haflen, hallfinngess, halflingis, haf(f)lins
To the extent of a half, half; in part, partially
quotes for this are much older (1225, He nis brute halflunge upo Godes rode)
craftyrat