Origin and history of Durham

"a hill of moderate elevation and more or less rounded outline," Old English dun "height, hill, moor," from Proto-Germanic *dunaz- (source also of Middle Dutch dunen "sandy hill," Dutch duin), "probably a pre-insular loan-word from Celtic" [Cambridge Dictionary of English Place-Names], in other words, borrowed at a very early period, before the Anglo-Saxon migration, perhaps from PIE root *dheue- "to close, finish, come full circle."

The more general meaning "elevated rolling grassland; high, rolling region not covered by forest" is from c. 1400. Specifically of certain natural pastureland districts of south and southeast England (the Downs) by mid-15c.

The non-English Germanic words tend to mean "dune, sand bank" (see dune), while the Celtic cognates tend to mean "hill, citadel" (compare Old Irish dun "hill, hill fort;" Welsh din "fortress, hill fort;" and second element in place names London, Verdun, etc.). German Düne, French dune, Italian, Spanish duna are said to be loan-words from Dutch.

"small island in a river; river meadow," late Old English, from Old Norse holmr "small island," especially in a river or bay, or cognate Old Danish hulm, from Proto-Germanic *hul-maz, from PIE root *kel- (2) "to be prominent; hill." Obsolete, but preserved in place names, where it has various senses derived from the basic one of "island:" "'raised ground in marsh, enclosure of marginal land, land in a river-bend, river meadow, promontory'" ["Cambridge Dictionary of English Place-Names"]. Cognate Old English holm (only attested in poetic language) meant "sea, ocean, wave."

one of the most etymologically complex of English place names, it illustrates the changes wrought in Old English words by Anglo-French scribes who could not pronounce them. Recorded 1016 as Scrobbesbyrig, it originally may have meant "the fortified place in (a district called) The Scrub." The initial consonant cluster was impossible for the scribes, who simplified it to sr-, then added a vowel (sar-) to make it easier still.

The name also changed due to Anglo-French loss or metathesis of liquids in words containing -l-, -n-, or -r- (also evident in the derivatives of Old French Berengier "bear-spear" — Old High German Beringar — name of one of the paladins in the Charlemagne romances and a common given name in England 12c. and 13c., which has come down in surnames as Berringer, Bellanger, Benger, etc.). Thus Sarop- became Salop- and in the 12c. and 13c. the overwhelming spelling in government records was Salopesberie, which accounts for the abbreviation Salop for the modern county.

During all this, the Anglo-Saxon inhabitants (as opposed to the French scribes) still pronounced it properly, and regular sound evolutions probably produced a pronunciation something like Shrobesbury (which turns up on a 1327 patent roll). After a predictable -b- to -v- (a vowel in the Middle Ages) to -u- shift, the modern spelling begins to emerge 14c. and is fully established 15c. A Shrewsbury clock (1 Hen. IV) for some reason, became proverbial for exactness, and thus, naturally, proverbial as indicating exaggeration of accuracy.