Early-attested site in the Parish of Horsley
- Har(e)stan(e) 1200,1201,1202,1203 P 1203 Cur 1204 CartAnt 1204 LibR 1206,1207,1209 P 1347 DbCh
- Harestain 1226 FF
- Har(e)ston(e) 1269 Ass Ed1 DbCh 1325 WollCh 1472 et passim
- Hor(e)stan 1226 ClR 1247 Lib 1258 BurtAn 1347 Pat
- Hor(e)ston(e) c.1200 RegAnt 1264,1279 Pat 1279 Fine 1291 Tax 1299 Ipm 1610 Speed
- del Castell de Horsel' 1373 Cor
'Grey stone', v. hār 2 , stān . Presumably the castle was built at a place called Harstan ; this is to be preferred to the popular theory that the name is descriptive of the castle itself. The change to Horsley Castle is late but note John del Castell de Horsel '1373Cor .