The second Psalm of each book has to do with the enemy. See App-10.
Why. ? Figure of speech Erotesis. App-6. Repeat at beginning of Psalms 2:2. Compare Acts 4:25; Acts 4:26.
heathen. nations. Note the quadruple Anabasis (App-6): nations, peoples, kings, rulers. Compare Psalms 1:1.
rage. tumultuously assemble.
people. peoples.
imagine. Same as meditate in Psalms 1:2.