Up in the sky; also, in heaven. For example, They fixed their eyes on high, looking for the comet, or, in the Bible (Psalms 63:5), "The Lord our God who dwelleth on high." [c. 1200]
In a position of authority, as in Those on high have decreed that we work every other weekend. This usage is an ironic transfer from def. 1. Also see powers that be.