yam ‧ mer /ˈjæmə $ -ər/ BrE AmE ( also yammer on ) verb [intransitive]
[ Date: 1400-1500 ; Origin: yomer 'to talk quietly, be sad' (12-15 centuries) , from Old English geomrian ]
informal to talk continuously in a way that is annoying:
a crowd of yammering aunts and cousins