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.
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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