Mark Amsler, senior English lecturer at the University of Auckland explains.
The original Christian saint of secret gift-giving and children was St Nicholas, a fourth-century Greek bishop, whose feast day is December 6. Later German Catholics called him "Sankt Niklaus", the Dutch "Sinterklaas". But it was early Americans who shaped our modern image of Santa Claus and coined the new name.
Long associated with St Nicholas' day, not Christmas Day, the gift-giver was first mentioned as "Santa the Claus" in a 1773 magazine, Rivington's Gazette, published in New York City: "Last Monday, the anniversary of St Nicholas, otherwise called Santa the Claus, was celebrated at Protestant Hall, at Mr Waldron's; where a great number of sons of the ancient saint, the Sons of Saint Nicholas, celebrated the day with great joy and festivity."
On the eve of American independence, the sons of St Nicholas were political - "Santa the Claus" was the product of anti-British sentiment in New York. After the Revolution, in his History of New York (1809), Washington Irving satirically referred to his Dutch pipe-smoking sailor with a big belly and a green coat as Santa Claus.
But a crusty Dutch sailor wouldn't do.
So in the mid-19th century cartoonist Thomas Nast depicted Santa Claus in Harper's Weekly as a jolly, red coated, pipe-smoking and bearded giver of gifts.