From The Oxford English Dictionary:

 Claddagh, n.

. . . .

A symbol consisting of two hands holding a crowned heart, which represents friendship, love, and loyalty. Chiefly attrib.: designating jewellery bearing this symbol.

Claddagh ring n. a ring given traditionally in Ireland as a token of love, freq. worn (with the symbol pointing inwards) to indicate that the wearer is married or engaged.

. . . .

1922 J. Joyce Ulysses iii. xviii. [Penelope] 713 He gave me that clumsy Claddagh ring for luck.

Link to the rest at The Oxford English Dictionary