The map shows where settlement or parish place-names which are of Scandinavian language origin are mainly found. In some cases, the entire name is Scandinavian, in others it is a hybrid – part English, part Scandinavian. Some names are the result of Scandinavian re-naming of English settlements, making them easier for speakers of Old Norse to pronounce (for instance, Shipton became Skipton. Cheswick became Keswick). Common Scandinavian elements in place-names are: -by, -thorp, -trop, or -thorpe, -toft, -tofts, -thwait or -thwaite, -holm or -holme, and ness.
See also this page about place names in the Danelaw.
It can be seen that some parts of the Danelaw have few or no Scandinavian place-names. How do explain this? (Clue: Examine maps which show the physical geography of these areas.)
This post is also available in: Norwegian Bokmål