Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
GAPP
As described in historical dictionaries
Patronymica Britannica (1860)
GAPP. From residence near some gap or pass. In the chalky cliffs of Sussex many places are so called, as Birling Gap,
Origin: English
Region of origin: British Isles
Country of origin: England
Religion of origin: Christian
Language of origin: English