2 things:  I thought it was pretty much slam-dunk that it was rickets and I did not know that about the earlier partof the 19th century. What a shame.

I saw a program (I think on the History Channel) about the re-birth of Christmas in America.  As mentioned above, in Colonial times it had fallen out of favor.  This was in part due to the pagan origins, but mostly because its associated vandalism.  It was the custom for people, called rowdies (as I recall) to go from house to house demanding food and drink.  They would break windows, etc. of those who failed to feed them.  Even if provided food and drink they would often still destroy property, partly on purpose and partly, in their often drunken state, with their boisterous partying.In the United States much of the re-birth of Christmas goes to Clement Clarke Moore, who in 1823 wrote "A Visit from St. Nicholas", also known as "The Night Before Christmas" and "'Twas the Night Before Christmas."  His poem was based upon classical legends, mostly notably that of the four centaury Greek Bishop canonized as Saint Nicholas.  He was famed for gifts to the poor.Our conception of Santa Claus is also heavily influenced by Thomas Nast the well known illustrator and political cartoonist.  (As well as devising the image of Santa Clause, Nast developed the image that today is associated with Uncle Sam as well as the donkey for the Democratic party and elephant for the Republican party.)  For example, the idea of Santa Claus checking his list to see who has been naught and nice comes from one Nast’s illustrations.  (He produces one every year over a considerable period of time.)The Christmas tree is an old German custom.  It became popular in Great Britain during the Victorian era when Price Albert set one up in Buckingham Palace.  In time the custom came to America.