E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Trinoda Necessitas.
The three contributions to which all lands were subject in Anglo-Saxon times, viz.(1) Bryge-bot, for keeping bridges and high roads in repair; (2) Burge-bot, for Fyrd, for maintaining the military and keeping fortresses in repair; and (3) naval force of the kingdom.