ETYMOLOGY
from wag (vb.) + tongue (n.)
EXAMPLE
“…but now indeet her tongue is loosened, and she talks, yes indeet, she does talk nineteen to the dozen and more. A silent woman she was. It is the nearest approach to a miracle I ever care to see. A chatterbox she is, and worse – a regular woman wag-tongue, a regular woman wag-tongue. I cannot get in a word edgeways now …”
From: Macmillan’s Magazine
Volume LXXXVI, May to October,1902
A Woman Wag-tongue
Lexicophilia 