What Does The Phrase "Watch Your Top Knot" Mean?

It basically means to take care of yourself and watch your head. Back in the day when people were afraid of Indians scalping them, they would say to a friend "watch your top knot".

I would think it would mean keep you eye on the goal (reaching the top knot) but not sure.

Do you know "Woody Woodpecker" the cartoon character?
That was a "Top Knot" on his head!
The Indian were scalped by White men first to collect the money that was offered, BY THEM!
Then they started cutting off certain male parts to make Tobacco pouches that brought BIG Money in town!
NOW you say the Indian was cruel! What color are YOUR CLOUDS where you live?

They need to repay us, as they do the Jews!

I believe it is a form of a cautioning good-bye.  Scalping may be plausible but I believe the term, as used in the movie "Jeremiah Johnson", refers to the last knot tied on a diamond hitch.  If that knot becomes undone the diamond hitch will come apart and your pack animal load will fall off that animal.  So, watch your top knot and good-bye.