Definition of "noggin"

Here Nat Adams, the burly bar-keeper, dispensed bad whisky at the rate of two shillings a noggin, or a guinea a bottle…

1889, Arthur Conan Doyle, The Parson of Jackman's Gulch

I needed some nails for to rivet them down...When you go to town you can buy the full noggin but beware you bring none of your fancibles home.

1999, “Bold Doherty”, in Midsummer's Night‎, performed by Dervish

I don’t know whether any of you, gentlemen, ever partook of a real, substantial, hospitable Scotch breakfast, and then went to a slight lunch of a bushel of oysters, a dozen or so of bottled ale, and a noggin or two of whisky to close up with.

1836 March – 1837 October, Charles Dickens, chapter 49, in The Posthumous Papers of the Pickwick Club, London: Chapman and Hall, […], published 1837

Or maybe he bumped his noggin when he fell down—after he got clipped on the legs.

2003, James D. Doss, Dead Soul‎

She bumped her noggin on the bulkhead above the doorway, smiled in apology for her presumed clumsiness.

2003, John Farris, The Fury and the Power‎