Its source is ri, a Gaelic name meaning "King."
The evolution of this English personal name can be traced through the Irish surname O'Ryan and its Irish Gaelic ancestors O Maoilriain and O Riain. These seem to have been based on the Irish Gaelic personal name Rian, but that name's derivation from ri, meaning ''king,'' is not certain. (One authority suggests ''water'' as an ultimate meaning.)
Though the surnames O'Ryan and Ryan have long been found throughout the English-speaking world, the personal name Ryan is a phenomenon of the mid-20th century. Its popularity was likely boosted by American actor Ryan O'Neal, born Patrick Ryan O'Neal in 1941.