Talked too much or said things without thinking; chattered foolishly.
From Middle English 'blaberen,' likely imitative in origin, mimicking the sound of loose talking. Related to 'blabber mouth' and similar formations.
The word 'blabber' is onomatopoeia—it actually sounds like what it means! Say it out loud and you can hear the loose, rambling quality of someone who talks too much.
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