also: くちはわざわいのもん
expression
words can lead to disaster; the tongue is the root of calamities
Proverb warning that careless speech invites trouble. Often used as a caution against gossip or thoughtless remarks. Compare with 口は災いの元 (same meaning).
See also: 口は災いの元
口は災いの門というから、余計なことは言わないほうがいい。
They say the mouth is the gate of calamity, so you'd better not say unnecessary things.
彼は口は災いの門を地で行くような人だ。
He's the kind of person who really lives out the proverb 'the mouth is the gate of calamity.'
Same meaning; 元 (source) is more common than 門 (gate). Both are interchangeable proverbs.
A Japanese proverb of uncertain origin, likely derived from the idea that the mouth is an opening through which trouble enters or exits, similar to sayings in other cultures.