Gaelic first names chiefly hail from 5 linguistic layers, Goidelic and 4 others, coinciding with the main languages of contact: Latin, Norse, Anglo-Norman and Scots.
Some names which did not acquire currency outside the Gaelic-speaking world were roughly transliterated into English, such as Gorm(sh)uil which is often rendered as "Gormelia".
This includes Oighrig which was equated with Euphemia or Henrietta, Dìorbhail with Dorothy, Beathag with Rebecca or Sophie.
In the case of women, the word nic is used, a shortening of the full phrase nighean mhic "daughter of the son of").
[3][a] Various other morphological changes (such as lenition or slenderization) may apply in Gaelic, so the surname MacDonald for example may appear as MacDhòmhnaill, MhacDhòmhnaill, MhicDhòmhnaill, NicDhòmhnaill depending on the grammatical context.
In speaking, ua/ó in names became reduced to [ə], as happened also in Northern Irish and Manx, and disappeared from Anglicised forms.
As a result of misspellings, one Gaelic surname often corresponds to numerous English/Scots forms, e.g. MacDhonnchaidh "son of Duncan" may appear as: Donagh(y), Donnagh, Dono(u)gh, MacConachie, MacConachy, MacConaghy, MacConchy, MacConechie, MacConkey, MacConnachie, MacConnechie, MacConnichie, MacConochie, MacConoughy, MacDona, MacDonachie, MacDonachy, MacDonaghy, MacDonaugh, MacDonnach, MacDonnagh, MacDonnoghie, MacDonogh, MacDonoghue, MacDonough, MacDunphy, MacKonochie, MacOnachie, MacOnechy, MacOnochie, Donohue or Donohoe (ignoring the Mac/Mc variation).