فَمَا لَبِثَ أَنْ رَجَعَ مُتَدَهْدِهًا وَتَقَهْقَرَ مُقَهْقِهًا
He soon returned, swaying with mirth and stepping backward in peals of laughter.
The forms mutadahdihan / muqahqihan carry conspicuous internal repetition. The returning messenger moves and laughs in an exaggerated manner, giving the sentence a tumbling comic energy.
One should not assign a universal emotional value to each consonant. It is the coincidence of repeated sounds with the described laughter and movement that produces the effect here. Sonic performance signals that something remarkable happened, but it does not yet tell the reader exactly what.