Psalm 2/Notes/Lexical.v. 1.577261

The first verb of the psalm (רָגַשׁ) occurs only here in the Hebrew Bible, and so its meaning is unclear. There are two main options:

• "assemble" (NJPS) >> "conspire" (NIV, NRSV; cf. CEV, GNT). So SDBH: "action by which a relatively large number of people form a group in order to pursue a common goal together."
• "rage" (KJV, ESV, CSB); also "are... angry" (NLT), "in turmoil" (REB), "in an uproar" (NASB)

The meaning "assemble" is based on an Aramaic cognate (רגשׁ aphel stem) that means "to gather together urgently." But the Aramaic verb only has this meaning in the aphel (= hiphil) stem. In the basic stem (= qal), the Aramaic verb means "to rage, be upset." The word רגשׁ (hithpael, niphal, and qal) occurs with this sense in some later Hebrew texts:

• "against me the assembly of the wicked rages (תתרגש), and they roar (ויהמו) like stormy seas when their waves crash (בהרגש)" (1QH^a col. 10, line 14. DJD vol. 40, p. 132, 142).
• "when the waves and the breakers of the waters surge up (ויתרגשו) on high with their noisy roar (המון)" (1QH^a col. 11, line 16-17. DJD vol. 40, p. 155).
• "Lo, heaven and the highest heaven, the abyss and the earth, tremble (σαλευθήσονται = ירגשו?) at his visitation!" (Sirach 16:18, NRSV; cf. Ben Sira Ms A 16:18. which reads כרגשו—"when he rages")

Interestingly, in the first two of these passages, the "raging" wicked are likened to the tumultuous sea, an image which we find elsewhere in the Psalter (see esp. Ps 46). This would be a fitting image for the nations in Ps 2 as well.

Note that verbs for anger also occurs in the last verse of Ps 2 (יאנף...יבער אפו), thus forming an inclusio.
The use of an Aramaic word at the beginning of the psalm might be a deliberate rhetorical device: the psalm deals with events of international significance, so it makes use of the international language of Aramaic. (Note other Aramaisms in vv. 9, 12. Compare also the use of Aramaic in Dan 2-7 where the content also concerns international politics).