Son of Maud; or, son of Matthew
Maddyson is a modern creative spelling of Madison. It originated as an English surname meaning 'son of Maud' (a diminutive of Matilda) or occasionally 'son of Matthew'. While the 'son of' suffix was literal in its surname origins, it has been used almost exclusively as a feminine given name in the United States since the 1980s.
Less common today
Maddyson isn't in the latest US Top 1000. It last peaked at #2,609 in 2009.
US births per 5-year period, 1990βpresent (SSA data).