ar.khu.vah refers to knees in the scene where they knock against each other in alarm.

The attested use names the knees in a scene of bodily alarm, where they knock against each other.

1. knees trembling in alarm · dominant

   In Daniel 5:6, the feminine plural construct form occurs in the clause describing the king's physical reaction after his thoughts alarm him; the APB renders the outcome as “his knees knocked against each other.”

   Daniel 5:6

In the Anselm Project Bible: In Daniel 5:6, the APB presents the clause as “his knees knocked against each other.” It confirms the scene without isolating every element of the original wording.