Green’s Dictionary of Slang

1. a ribbon.

1753		J. Poulter Discoveries (1774) 42: A Lobb full of Glibbs; a Box full of Ribbons.
1786		Whole Art of Thieving [as cit. 1753].

2. loquacity, verbosity.

1821		J. Burrowes Life in St George’s Fields 10: As he is very full of glib, you must let him have all the jaw-work to himself.
1905		‘Doss Chiderdoss’ ‘When Duty Calls’ Sporting Times 13 May 1/3: That burglar was a wily man, whose conversation glib / Put poor Slobber into such a helpless state / That he found himself assisting in the cracking of the crib.

3. the tongue; thus slacken your glib, loosen your tongue [resemblance to sense 1; but note SE glib, voluble but essentially trivial].

1845		G.W.M. Reynolds Mysteries of London vol. 2 142: Slacken your glib. Loosen your tongue.
1864, 1867, 1870		Hotten Sl. Dict. 144: GLIB, a tongue; ‘slacken your glib,’ i.e., ‘loosen your tongue.’.
1895		Crowe Aus. Sl. Dict. 32: Glib, a tongue, ‘slacken your glib,’ i.e., loosen your tongue.
1937–84		Partridge DSUE (1984) 470: c. mid-C.19–20.