Early-attested site in the Parish of Holsworthy
- Rit(t)hedon 1238 Ass 1330 SR
- Ritherdon 1281 Ass 1333 SR 1391 FF
- Ryderdon 1428 FA
In spite of the absence of u -forms we are probably right in interpreting this as 'cattle-hill,' from OE hryðer and dun.