mainly

adverb

1. chiefly; principally; for the most part; in the main; to the greatest extent: Our success was due mainly to your efforts. The audience consisted mainly of students.
2. Obsolete. greatly; mightily; abundantly.

adverb

1. for the most part; to the greatest extent; principally
2. obsolete strongly; very much

adv.late 13c., “vigorously,” from main (adj.) + -ly (2). Meaning “especially” is from c.1400; that of “for the most part” is from 1660s.