sū
This prepositional particle denotes location at, in, or on somewhere. In the Babel text, the phrase sū jekiēn xīnār is a prepositional phrase headed by sū. jekiēn means land, and xīnār is a representation of the proper name Shinar. So sū jekiēn xīnār is “in the land of Shinar”. The second clause (ñatta jamāesa japōññe sū jekiēn xīnār) of the second sentence (il ñatta jarēþa rūānnie il ñatta jamāesa japōññe sū jekiēn xīnār il aþ ñatta āke jamāramma;), therefore, is “they found a plain in the land of Shinar”.