From Robert Kirk’s glossary in The Secret Commonwealth, written in the seventeenth century (page 76 of the NYRB edition):
Elves: A tribe of the fairies that use not to exceed an ell in stature.
So how tall is an ell? According to this helpful page of conversions:
1 ell = 114.3 cm = 45 inches = 3.75 feet = 5 spans
It’s interesting to see this meaning actually encoded in the name, despite the fact that the tall Norse elf (the álfar) has become dominant via the works of Tolkien.
Also related, over at Strange Magic: Monster Makeover: Elves (though I prefer my faeries to have more sinister and less German peasant).
|AD&D Monster Manual page 40|