Sources

“A difficult name. PNS 151 suggests ‘field of slander’ v. G. dail thuaileas in a locative form, and SPN 173 ‘valley of the wood’ v. G. dail choillidh, but neither interpretation is tenable phonologically. CPNS 458 cites the Aberdeenshire Fowlesy as a probable diminutive of G. foglais ‘sub-stream’ v. fo ‘under’, glais ‘stream’, and Derwesy, Dalwussy, Dalwlsy and the local pronunciation (dawi:si) are possible parallels of the Aberdeenshire form. The termination may represent either a diminutive: ‘field of the streamlet’ v. dail glaisidh, or G. innis ‘a meadow-haugh’, dat. –isidh (silent dh) in unstressed position at the end of names, ‘field of the river-haugh’ v. dail glaisisidh.” Dixon, 150