In sewing and crafts an embellishment is anything that adds design interest to the piece
http://en.wikipedia.org/wiki/Embellishment[/quote]
For whatever reason, the design personally appealed to the person who put it there. Like almost any personal work of art, it may simply be a unique adornment that's one of a kind. Perhaps its only purpose is for someone to notice it and to appreciate the fact that it exists.
It's also possible that the person carved their initials into an artwork resembling the stylized branches of a tree.