From the experts:
This ancient royal Scottish name and its equally-correct spelling French variation Stuart had a brief vogue in midcentury America--it was Number 286 in 1955--dropped off the list completely in the nineties.
The Stuart version was introduced to Scotland by Mary Stuart, Queen of Scots, who grew up in France. As a surname, it was an occupational appellation for someone who served as a steward in an aristocratic or royal household. Stewart and Stuart started being used as first names in the early nineteenth century. One current bearer is Stewart Copeland, best known as the drummer for the band the Police.
NIckname Stewie is not a plus--just think Stewie Griffin on Family Guy.