Niamh, derived from the Old Irish Niam, is an ancient Irish name that was originally a term for a goddess. In Irish myth, one who bore it was Niamh of the Golden Hair, daughter of the sea god, who falls in love with Finn's son Oisin and takes him to the Land of Promise, where they stayed for three hundred years. Niamh can be Anglicized as Neve, Nieve, or Neave.

Nainsí is the Irish Gaelic form of Nancy, showcasing the distinctive spelling conventions of the Irish language. The original name Nancy developed as a medieval diminutive of Anne, which comes from the Hebrew Hannah meaning 'grace.' In Irish form, Nainsí maintains the same pronunciation as Nancy while connecting the bearer to Irish linguistic heritage. The name represents the beautiful adaptation of imported names into traditional Irish spelling patterns, a process that helped preserve cultural identity through centuries of external influence. Though not among the most common Irish names today, Nainsí might appeal to families with Irish roots seeking to honor their heritage while using a name that remains recognizable across cultures.

Nollaig is a unisex Irish name, created in the 20th century as a translation of the French name Noel. Meaning "Christmas", or more generally "December", it is also used in Irish as the name of the month, just as April and June may be used in English.