Who might this Cushi have been?

Zephaniah is called the son of Cushi. Cushi is a proper name related to the title Cushite and the place Cush. Cush was the name of ancient Ethiopia (located in modern Sudan). “We know that Judah made a number of political alliances with the nation of Cush prior to Zephaniah’s ministry (Isaiah 18:1–2; Isaiah 20:5–6) and that Jerusalem’s leadership had strong ties with Cushites (2 Samuel 18:21; Jeremiah 38:7; Jeremiah 39:16)."¹ Zephaniah gives special attention to the Cushites (Zephaniah 2:12) and Cush (Zephaniah 3:10) in his declarations of punishment and restoration. Some say this adds to the likelihood that Zephaniah was a biracial Jew.

But even though Zephaniah twice mentions the land of Cush (Zephaniah 2:12; Zephaniah 3:10), there is no reason to interpret Cushi as a reference to Ethiopian heritage. Cushi is used as a proper name in another genealogy, in Jeremiah 36:14, and Cush the Benjamite is mentioned in Psalm 7:1. R.K. Harrison indicates that there appears to be little ground for the supposition…that Cushi his father was actually an Ethiopian, and that Zephaniah was a Negro slave in the service of the Temple.² Many conclusions reached regarding this distinctive name fall into the realm of speculation.