The God Of gods
Psalms 136:2: O give thanks unto the God of gods: for his mercy endureth for ever. 3 O give thanks to the Lord of lords: for his mercy endureth for ever.
The translators who capitalized one word but not the other knew what they were doing.
Treasury Of David on Psalms 136:2:
O give thanks unto the God of gods. If there be powers in heaven or on earth worthy of the name of gods he is the God of them; from him their dominion comes, their authority is derived from him, and their very existence is dependent upon his will. Moreover, for the moment assuming that the deities of the heathen were gods, yet none of them could be compared with our Elohim, who is infinitely beyond what they are fabled to be. Jehovah is our God, to be worshipped and adored, and he is worthy of our reverence to the highest degree. If the heathen cultivate the worship of their gods with zeal, how much more intently should we seek the glory of the God of gods -- the only true and real God. Foolish persons have gathered from this verse that the Israelites believed in the existence of many gods, at the same time believing that their Jehovah was the chief among them; but this is an absurd inference, since gods who have a God over them cannot possibly be gods themselves. The words are to be understood after the usual manner of human speech, in which things are often spoken of not as they really are, but as they profess to be. God as God is worthy of our warmest thanks.
Deuteronomy 10:1: For the LORD your God is God of gods, and Lord of lords, a great God, a mighty, and a terrible, which regardeth not persons, nor taketh reward:
Deuteronomy 10:17: For the LORD your God is God of gods, and Lord of lords, a great God, a mighty, and a terrible, which regardeth not persons, nor taketh reward:
Joshua 22:21: Then the children of Reuben and the children of Gad and the half tribe of Manasseh answered, and said unto the heads of the thousands of Israel, 22 The LORD God of gods, the LORD God of gods, he knoweth, and Israel he shall know; if it be in rebellion, or if in transgression against the LORD, (save us not this day,) 23 That we have built us an altar to turn from following the LORD, or if to offer thereon burnt offering or meat offering, or if to offer peace offerings thereon, let the LORD himself require it;