Lugmad (or occasionally Lugbad) was the normal spelling in Old Irish. It is a closed compound consisting of Lug (understood to be a pre-Christian Celtic God) + an unclear generic. Dónall Mac Giolla Easpaig ('Noun + Noun conpounds in Irish placenames', 162-3) explains the second element of this placename as follow: 'There is an o- stem which could possibly suit the context here. This is moth (later mod) which was used by the native grammarians to denote the masculine gender but which originally referred to the male member ... The name Lugmad probably referred originally to a mound or standing stone at which Lugh was commemorated'.

It is clear that the internal consonant cluster -ghmh-/-ghbh- (in Modern Irish orthography) dissapeared in this placename during the course of the 13th century, as reflected in contemporary English forms of the name such as Luueth (bliain 1235) agus Loueth (O’Rahilly 1930: 176). The rhyme pattern of poetry composed in the area in the 18th and 19th century further demonstrates that it was then pronounced as Lú despite the various spelling variations found at that time. Note the following example found in the syllabic poetry of Art Mac Cumhaidh, 'Dís ó Lú agus triúr ón Éirne, or the following example of such composition by Risteard Taath who died in 1736:

Aithris dod’ mháighistir go glic,
A leabhráin bhric, go raibh tú i Lúgh’,
Go dtugais damh-sa sgéal Ádhamh.
Cia an lá do bhlas an t-ubhall.

(Ó Tuathail 1923: 60)