Element Meaning

ON nom. sg. obscure element + gen. sg. dalr, masc. ‘valley’

Sources

Eilean Eisdeil: Fionn, Kilbrandon and Kilchattan Names, part vii
Eisdeal: Robertson MS405
Eysdale I: 1750 Dorret
Eisdeal: Henderson 1910, 188
Èisdeal: Stòrlann map

Eisdeal called of old Fraoch-eilean: Robertson MS371, 266 [the capital E has a brave and and acute on it, which denotes an open short e. On the line above he uses the same diacritics for the word beithe, ‘birch’]