If someone swills their drink, they're sloshing it around (often in their own mouth). As gargling is to the throat, swilling is to the mouth. If a lie is "well-swilled", it's been rolled around in the liars mouth thoroughly before being spat out on you.

If someone swills their drink, they're sloshing it around (often in their own mouth). As gargling is to the throat, swilling is to the mouth. If a lie is "well-swilled", it's been rolled around in the liar's mouth thoroughly before being spat out on you.