Sirens were bird-like women, not unlike Harpies, who lured sailors with their songs. They had various names and their numbers also varied, as did their parents. Traditionally, they lived on the island of Anthemoëssa ('flowery') near the straits where Scylla and Charybdis lurked. They are first mentioned in the Odyssey, where Odysseus is told, 'your next encounter will be with the Sirens, who bewitch everybody that approaches them'.

Their name is of uncertain origin, but is popularly derived from seira, 'chain', for their 'binding' power. (In Greek the name is spelt Seirenes, singular Seiren.) There is a theory, however, that traces their name back to seirios, 'hot', 'scorching', which was a word used of heavenly bodies causing heat (compare Sirius).

This might mean that the Sirens had some sort of power to dry up pastures in the hot summer months. Plato divided the Sirens into three categories and assigned them as being under the rule of Jupiter, Neptune and Pluto respectively.

The modern ship's or factory siren is named after them, and the word was specially chosen for the first siren, invented by the Frenchman Cagniard de la Tour in 1819 ('The Syren, a new Acoustical Instrument... In consequence of this property of being sonorous in the water this instrument has been called the Syren').

The word was in general use in English before this, however, to mean 'dangerously seductive woman'. The mythological Sirens have often been popularly confused with mermaids, which of course they are not: Sirens were half-woman, half-bird; mermaids were half-woman, half-fish.