Is a “Santa Rally” really thing?

Has the stock market really done better going into Christmas? I hear people mention the santa rally all the time but I just wonder if that’s really a trend that’s occurred much in the past or if people are just hopeful and want to remark on Christmas.
Why would people buy more stocks around the holidays? It’s not like you can put them under the tree for a Christmas present haha. Don’t people want to tax loss harvest during this time of year and sell?