A tributary was a rent payer. 29 of the 31 occurrences of this word in Domesday Book were in circuit 6, in the counties of Derby, Lincoln, Nottingham and Yorkshire. Most occurred on manors in need of re-development, many on manors which had been wasted or had suffered a sharp decline in their value since the Conquest, as at Burton Agnes, where it was recorded that the manor had been worth £24 in 1066 but 'now 1 tributary pays 10s to the King'. There may be an implication, therefore, that tributaries were colonisers, or re-developers.
For further information, see Susan Reynolds, Fiefs and vassals: the medieval evidence reinterpreted (1994).