"of or pertaining to elves," 1590s, from elf; first found in Spenser, who also used it as a noun and might have been thinking of elven but the word also is a proper name in the Arthurian romances (Elphin).
1. She was an elfin-like girl who looked barely 10 years old.
2. The cheap music turned elfin and lovely.
3. All the little creatures joined in the elfin dance.
4. She was an elfin creature -- graceful and delicate.