blab ‧ ber ‧ mouth /ˈblæbəmaʊθ $ -ər-/ BrE AmE noun [countable]
[ Date: 1900-2000 ; Origin: blabber 'person who talks too much' (16-21 centuries) (from blab ) + mouth ]
informal someone who tells secrets because they always talk too much
blab ‧ ber ‧ mouth /ˈblæbəmaʊθ $ -ər-/ BrE AmE noun [countable]
[ Date: 1900-2000 ; Origin: blabber 'person who talks too much' (16-21 centuries) (from blab ) + mouth ]
informal someone who tells secrets because they always talk too much
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012