Reilly ranks at #881 with 134 entries, registered male. The name is an Anglicization of the Irish O'Raghallaigh, an old Connacht surname meaning descendant of Raghallach. On a pet registry Reilly functions as one of the cleaner Irish-surname-as-given-name picks, sitting alongside Murphy, Quinn, and Finn.
The Irish-surname-as-given-name register
Reilly clusters with Finn, Murphy, Rooney, and Quinn in the Irish-surname male pet pocket. Many owners pick the name because there is family heritage in it, but a meaningful slice pick it for sound alone — the bouncy diminutive feel paired with a pedigreed surname texture.
Breed lean and sound
The name lands hardest on Irish-origin breeds and red-coated dogs: Irish Setters, Goldens, and red mixed breeds. Two syllables, front-stressed (RYE-lee), with the long open RYE-vowel and bouncy ending. Excellent recall shape, distinct from common command words.
The counter-reading
The honest consideration: the Reilly versus Riley spelling decision is a coin-flip that owners have to commit to at registry time, and either spelling will be misread occasionally. Reilly is the more traditionally-Irish spelling; Riley is the more modern English form. The human Reilly page shows mid-tier SSA presence with the spelling holding steady.