Meaning

verb state categorically

verb to declare or affirm solemnly and formally as true

verb insist on having one's opinions and rights recognized

originFrom Latin assertus, perfect passive participle of asserō (“declare someone free or a slave by laying hands upon him; hence free from, protect, defend; lay claim to, assert, declare”), from ad (“to”) + serō (“join, range in a row”).

Etymology from Wiktionary, CC BY-SA 3.0