Greysen is a modern spelling of Grayson, originally an English surname meaning 'son of Gray.'
Greysen is a stylized modern variant of the English surname-turned-given-name Grayson, which derives from the Middle English occupational designation for "the son of the steward" (from the Old French gris, meaning "gray," and the suffix -son). The steward, or "greyve," was a figure of considerable administrative importance in medieval England — managing estates, overseeing accounts, keeping order — and the surname Grayson carries within it this heritage of competence and responsibility. In its older usage, the name could also simply denote someone with gray hair, that most ancestral of physical descriptors.
Grayson as a given name surged in popularity in the United States during the 2000s and 2010s, riding the fashionable wave of surnames-as-first-names that also produced Mason, Jackson, Landon, and Brayden. By 2015, Grayson had broken into the top 20 boys' names in the US. The spelling variant Greysen — substituting the more continental "ey" digraph for "ay" and adding an "e" to the suffix — reflects the parallel trend toward personalizing spellings as a form of individual distinction.
The grey spelling also evokes the color more directly, with its sophisticated, weather-beaten English associations. Cultural visibility for the name received a boost through figures like Grayson Perry, the celebrated British artist and Turner Prize winner, whose work and public persona lent the name an association with creativity and intellectual boldness. For the Greysen spelling specifically, it signals parents who wanted the warm familiarity of Grayson with a slightly more bespoke touch — a name that is immediately readable, confidently masculine, and modern without being outlandish.