बाहुः' इति श्रुतेः ।महीं पूजां धरणीं वा धरति इति महीधरः ॥
In plain words
'...the arm' — so the śruti says. And mahī here means worship, or it means the earth; he carries either one. That is why he is called Mahīdhara, the bearer.
Close to the Sanskrit
'...the arm' — thus from the śruti. He bears mahī, that is, worship, or the earth — thus, Mahīdhara.