When hands in Kapitta hasta is held crossed at the wrists we get the Bhairunda hasta. Some times this hasta is done without crossing the wrists also. Hands in kapitta just join at the wrists.
Lets take a look at the viniyoga shloka (uses)
bhairunde pakshidampatyor bhaiundo uchyate karah.
In Sanskrit the word Bherunda or bhairunda means terrible. Therefore I think the wise men say this gesture is used to show the Bhairunda bird in the mythology who is an eagle with two heads and a single body. Must have been a weird looking creature !!!
It can also be used to show a pair of birds sitting together. In this case the hands are not crossed but only joined at the wrists.