Gold lunula (plural: lunulae) is the term used to describe a distinctive type of early Bronze Age necklace shaped like a crescent moon. Gold Lunula are found most commonly in Ireland, but there are moderate numbers in other parts of Europe as well, particularly Portugal and Great Britain. Although no lunula has been directly dated, from associations with other artefacts it is thought they were being made sometime in the period between 2200-2000BC (Needham 1996, 124). Less than two hundred gold lunulae are known and it is possible they were all the work of a handful of experts.

Source: Wikipedia.

A druid crowded in on me in my dream, black-bearded, hungry-eyed, foul-breathed, a gold lanula round his neck dangling and glittering above me.

Source: Gate of Ivory, Gate of Horn by Robert Holdstock.

From searching on the internet, the different spelling is common, but not official. ‘Lunula’ also refers to the pale, crescent shape at the base of a fingernail.