Jamieson, Fausset and Brown on Daniel 4:9

9. spirit of the holy gods--Nebuchadnezzar speaks as a heathen, who yet has imbibed some notions of the true God. Hence he speaks of "gods" in the plural but gives the epithet "holy," which applies to Jehovah alone, the heathen gods making no pretension to purity, even in the opinion of their votaries (De 32:31; compare Is 63:11). "I know" refers to his knowledge of Daniel's skill many years before (Da 2:8); hence he calls him "master of the magicians."

troubleth--gives thee difficulty in explaining it.