It’s the question on everyone’s lips, so let’s defer to acclaimed journal of urban geography Wikipedia:
The town takes its name from dic an Anglo-Saxon word meaning either ditch or embankment. Diss has a number of historic buildings, including an early 14th-century parish church and an 1850s corn exchange still in operation.
At the time of Edward the Confessor, Diss was part of the Hartismere hundred (a hundred was an administrative subdivision) of Suffolk, and it was recorded as such in the Domesday book. It is recorded as being in the king’s possession as demesne (direct ownership) of the Crown, there being at that time a church and a glebe of 24 acres.
that probably answers it!
wouldn’t know, didn’t bother reading it