Romanian word mai ales comes from Romanian mai, Romanian ales (Chosen, selected.)

Detailed word origin of mai ales

Dictionary entry	Language	Definition
mai	Romanian (ron)	(dialectal) liver May Mallet, maul, sledgehammer, rammer, club More.
ales	Romanian (ron)	Chosen, selected.
mai ales	Romanian (ron)	Especially; mostly.

Words with the same origin as mai ales