Abarim Publications' online Biblical Hebrew Dictionary
The verb ערק (araq), probably means to gnaw. It occurs only twice in the Bible, and that in the same chapter: Job 30:3 and 30:17. Comparing this verb to various cognates, indicates the meaning of a nagging, senseless sensation.
HAW Theological Wordbook of the Old Testament has nothing on the verb, but Klein's Etymological dictionary of the Hebrew Language reports relations to a similar (but extra-Biblical) verb meaning to flee (to go away).