ETYMOLOGY
from tongue (n.) + pad;
the second element is of uncertain origin, but possibly from pad (a robber a highwayman)
EXAMPLE
“… You shall have as good as you bring, at Billingsgate; not to say, worse. You’re a Whore, and you’re a Whore, is the Language of all Scolds, from an Oyster-Hussy to a Lady of Pleasure. ‘Twas pleasant enough to hear two Tongue-Pads a-scolding once, and giving one another the Lie: Why, says the one, Thou ly’st like a Punk, a Thief, and a Witch. …”
From: Moral Reflexions upon select British Proverbs: familiarly accommodated to the humour and manners of the present age
By Oswald Dykes, 1708
Lexicophilia 