The founder of Luxemburg's wife was said to have been a mermaid. She requested to have one day each month to herself where she would be alone, and once married, did this for years. Finally, her husband wanted to see what his wife was doing, and spied that she was a mermaid. Instantly she jumped through the window into the river and never returned.

In early medieval Irish Christianity, mermaids were said to represent the sins of vanity, pride and lust. The mermaids were a warning for all good Christians to avoid these sins and remain in the church

Once I sat upon a promontory,
And heard a mermaid on a dolphin's back
uttering such dulcet and harmonious breath,
That the rude sea grew civil at her song,
And certain stars shot madly from their spheres
To hear the sea-maid's music.

A Midsummer Night's Dream
William Shakespeare

In ancient Greece, Naiad's were beautiful water spirits who inhabited lakes, streams and rivers. These spirits protected their water from intruders, but could be placated with offerings tossed into their waves.

With the coming of Christianity, the Irish believed mermaids were pagan women transformed by St Patrick and banished to the sea.

It is now believed that marine animals such as the manatee are what gave rise to the legends of mermaids.

In Greek mythology, Sirens were creatures with the bodies of birds and the heads of women, and were the daughters of the sea god Phorcys. Their voices were so alluring that sailors would wreck their ships and perish to follow the siren's songs.

Mermaids are said to be guardians of women. In their wrath to right a wrong, they can bring storms and hurricanes to avenge a woman.