. This is a combination of Lug (the god Lugh) and násad (an assembly), which is unstressed when used as a suffix. Another theory is that it originated from the word nás (death), rather than násad. Later spellings include Lu?nasad, Lughnasadh and Lughnasa.

In Modern Irish, the spelling is Lúnasa , which is also the name for August. The genitive case is also Lúnasa as in Mí