Abarim Publications' online Biblical Hebrew Dictionary
The verbs עתן ('atan) and עתל ('atal) aren't used in the Hebrew of the Bible and it's by no means certain that they ever existed. That these verbs are supposed to have existed is because a small cluster of names appear to have been derived of them.
The formidable linguist Gesenius proposed that the verb עתן ('atan) was related to a similar Arabic verb that meant to deal violently with, and from which derived a noun that would literally describe a violent creature and was used to indicate the lion. Gesenius additionally concluded that עתל ('atal) is so closely related to עתן ('atan) that it essentially meant the same.
The equally formidable trio of linguists Brown, Driver and Briggs, who based their lexicon on that of Gesenius, disagreed with the latter's conclusions and equated the verb עתל ('atal) with an Assyrian verb atalu, meaning to be exalted or grow great.
It is, of course, not unthinkable that this Assyrian verb essentially conveyed the same kind of energy as the Arabic one, and that to the Arabs a violent lion was in fact a creature of signature greatness.