Abarim Publications' online Biblical Hebrew Dictionary
Scholars insists that when classic Hebrew was a spoken language, it must have contained two separate roots עדל ('dl) The reason that scholars believe that these roots were once used by Hebrew speaking people, even though none of the authors of the Bible actually incorporated them, is that the Bible contains two names that are obviously derived of these verbs. The name Adlai is one of them, and it's assumed it came from one version of עדל ('dl) The other name is Adullam, which is assumed to have been derived from the other version of עדל ('dl):
The verb עדל ('dl I) does not occur in the Hebrew Bible but scholars assume it is related to an Arabic verb that means to act equitably. Or else it might have to do with an Assyrian noun edlu, which means hero.
The root עדל ('dl I) also doesn't occur in the Hebrew preserved in the Bible, but scholars assume that this verb is kin to an Arabic verb meaning to turn aside.