120 At least six explanations for the name Iscariot have been proposed, but it is probably transliterated Hebrew with the meaning “man of Kerioth” (there are at least two villages that had that name). See D. A. Carson, John, 304.
121 Grk “this one”; the referent (Judas) has been specified in the translation for clarity.
122 This parenthetical statement by the author helps the reader understand Jesus’ statement one of you is the devil in the previous verse. This is the first mention of Judas in the Fourth Gospel, and he is immediately identified (as he is in the synoptic gospels, Matt 10:4, Mark 3:19, Luke 6:16) as the one who would betray Jesus.

In other versions

He spoke of Judas the son of Simon Iscariot, for he, one of the twelve, was going to betray him.

(He meant Judas, the son of Simon Iscariot, who, though one of the Twelve, was later to betray him.)

He was referring to Judas, Simon Iscariot’s son, one of the Twelve, because he was going to betray him.

He was speaking of Judas, son of Simon Iscariot, one of the Twelve, who would later betray him.

(Now he was speaking about Judas son of Simon Iscariot, because this one—one of the twelve—was going to betray him.)

He spake of Judas Iscariot the son of Simon: for he it was that should betray him, being one of the twelve.

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