expression, ichidan verb
to be a chatterbox from birth; to be born talking
Derogatory idiomatic expression used to describe someone who talks excessively, as if they were born with their mouth first. The literal meaning is 'to be born from the mouth'.
あの人は口から生まれたように、いつも喋っている。
That person talks all the time, as if they were born talking.
おしゃべり is a more neutral term for a talkative person or chatting, while 口から生まれる is a derogatory idiom emphasizing excessive talkativeness from birth.
The phrase is a figurative expression; the literal image is of being born from the mouth, implying an innate tendency to talk excessively. The exact origin is uncertain.