Apparently from H559 (in the sense of self exaltation); a summit (of a tree or mountain): - {bough} branch.
Verse
Matrix
2Sa 15:12And Absalom sent for Ahithophel the Gilonite, David's counsellor, from his city, even from Giloh, while he offered sacrifices. And the conspiracy was strongH533; for the people increased continually with Absalom.
Isa 28:2Behold, the Lord hath a mighty and strong oneH533, which as a tempest of hail and a destroying storm, as a flood of mighty waters overflowing, shall cast down to the earth with the hand.
Isa 40:26Lift up your eyes on high, and behold who hath created these things, that bringeth out their host by number: he calleth them all by names by the greatness of his might, for that he is strongH533 in power; not one faileth.