ETYMOLOGY
– from onycho- (relating to the nails) + –phagist (denoting people or animals who eat a particular food)
EXAMPLE
“…My eldest daughter had finished her Latin lessons, and my son had finished his Greek; and I was sitting at my desk, pen in hand and in mouth at the same time, (a substitute for biting the nails which I recommend to all onygophagists)…”
From: The Doctor &c.
By Robert Southey, 1834
“The Utility of Pockets. A Compliment Properly Received”
Lexicophilia 