The origin of Santa Claus is hundreds of years old and goes back a friar or monk named St. Nicholas, generally thought to be around 280 AD. Patara, near Myra in modern-day Turkey is the supposed location of the monk. Fast forward to the 1770s and St. Nick arrived in N. America through the Dutch Population. The Dutch called him Sinta Klaas. By the early 1800s, he began to be depicted in drawings and a few books, but he looked nothing at all like our modern day inage of Santa. By the 1890s, the Salvation Army sent out people dressed like Santa to collect funds and his image began to solidify.
To make a long story short, Santa began to be more and more popular and his likeness began to look like what we think of as Santa. Basically, you have a long evolution here of what Santa looks like that evolved with what Society thinks Santa looks like.
I do not believe in Santa, but if I was forced to say what he looks like, I reckon this would be it:
