Raigan is likely a modern spelling of Reagan, from an Irish surname meaning little ruler.
Raigan is a modern American elaboration of the Gaelic surname Reagan, itself derived from the Old Irish Ó Riagáin — "descendant of Riagán" — a personal name rooted in "rí," the Old Irish word for king. The Uí Riagáin were a powerful Munster dynasty in medieval Ireland, and the surname spread widely through the Irish diaspora.
The name entered American popular consciousness most dramatically through Ronald Reagan, the 40th President of the United States, whose surname had already begun its migration into first-name usage by the 1980s, appealing to parents who associated it with patriotism and authority. The distinctive spelling "Raigan" — replacing the traditional "ea" with "ai" — emerged as American naming culture shifted toward phonetic individualism in the late 20th and early 21st centuries. This orthographic creativity preserves the melodic Irish sound while giving the bearer a visually unique identity on the page. Today Raigan functions comfortably as both a masculine and feminine given name, sitting in the same stylistic family as Aidan, Caelan, and Brailey — names that wear Celtic roots with a distinctly American accent.