Early-attested site in the Parish of Ivinghoe
- Sebroc 1227 Ass
- Seibroc 1227 FF
- Seybroc 1241 Ass 1250 Fees
- Seybroke c.1250 Mert 1291 Ch 1292 Ipm 1346 FA 1348 Ipm 1355 Pat 1399 IpmR
- Saybroke 1284 FA
- Seibroke 1334 Ipm
- Seabrook 1625 Cheddington
A personal name *Sǣga (< *Sǣiga ) is suggested both by the forms above and by the early spellings of Seaton (Rutland)DB Seieton 1187 P Saieton . Names compounded with Sǣ -are common. The diminutive suffix -iga occurs in the 'heroic' personal name Wudiga, contracted in Widsith to Wudga. A similar contraction seems to have taken place here.
Alternatively Professor Ekwall would take the first element to be an OE sǣge , 'slowly moving' (cf. MLG sege , 'dripping, blear-eyed,' ON seigr , 'tough,' lit. 'dripping slowly') found in the compound on -sǣge , 'assailing.' The brook now forms part of the Grand Junction Canal, but judging by the lie of the land it can never have had much of a fall.