Etymology
From Old English Dūnholm, which is from dun (“hill”) + Old Norse holm (“islet, island”). In order to get from Dunholm to Durham, two major processes had to take place. Firstly, the n at the coda of the first syllable, dun, underwent dissimilation. Specifically, by influence of the m in the coda of the following syllable (holm), said n denasalised and lenited to the oral r, thus dur. Secondly, after a weakening of the vowel quality in the more weakly-stressed syllable holm, this ending was misanalysed as the similar-sounding toponymic suffix, -ham, meaning home or farm.
Doublet of Duresm and Dunelm.