🔼The name Susi in the Bible
The name Susi (which in Hebrew is not diminutive of Susan, by the way) occurs only once in the Bible. It's the name of the father of Gaddi of Manasseh, who joined the contingent of spies that Moses deployed to scout out Canaan (Numbers 13:11). This same contingent contained Hosea, whom Moses renamed Joshua.
🔼Etymology of the name Susi
The name Susi comes from the noun סוס (sus), meaning horse:
The letter י (yod) upon which our name ends, may either create an adjective (horse-like or belonging to the horse), a possessive form (my horse), or may be a remnant of יה (Yah) = יהו (Yahu) = יו (Yu), which in turn are abbreviated forms of the Tetragrammaton יהוה, YHWH, or Yahweh.
For a meaning of the name Susi, both NOBSE Study Bible Name List and Jones' Dictionary of Old Testament Proper Names take the final י (yod) to be an adjective maker and read Horseman.