*עֲשַׁשׁ (v. אָשַׁשׁ) to be strong.
Ithpa. - אִתְעַשֵּׁשׁ to exercise one’s strength. Midr. Till. to Ps. XIX, 1 מאבנא דהוא מִתְעַשֵּׁשׂ (בה) וכ׳ by the stone with which he practices you can tell his strength; [ed. Bub., a. Yalk. Ps. 672 מִתְגּוֹשֵׁשׁ, h. form, v. גָּשַׁשׁ].