Lower, Mark A (1860) Patronymica Britannica: a dictionary of the family names of the United Kingdom. London: J.R. Smith. Public Domain.
KEMPTHORNE
As described in historical dictionaries
Patronymica Britannica (1860)
KEMPTHORNE. The family name (which was originally Ley) was derived from an estate so called in the parish of Beer-Ferris, co. Devon. C. S. Gilbert's Cornwall.