English longbow
It has been suggested that 'thumbs up' was a signal from English archers preparing for battle that all is well with their bow and they are ready to fight. Before use, the fistmele (or the "brace height") was checked, that being the distance between the string and the bow on an English longbow. This fistmele should be about , which is about the same as a fist with thumb extended. The term fistmele is a Saxon word that refers to that measurement.