popular belief; common saying; folklore
Refers to a widely held but often unverified or unscientific belief, traditional saying, or piece of folk wisdom. Can carry a nuance of 'old wives' tale' or 'myth' when contrasted with fact.
That's nothing more than a popular belief.
This common belief has been scientifically disproven.
Compound of 俗 (ぞく, 'common, vulgar, popular') and 説 (せつ, 'theory, opinion, explanation'). The word itself is straightforward and transparent.