'To know what's what,' is to know the nature of things, or as we classically express it, 'to be up to a thing or two.'
I know what's what. I know on which side my bread is buttered.--Ford, The Lady's Trial, II. 1.
I knew the time would come when they would say I knew what was what.--Maj. Downing's Letters, p. 190.
A tame, vacant, doll-faced, idle gall. What a fate for a man who knows what's what.--Sam Slick, 2d series.
Why, Mr. Bott, if I wasn't a married man, I'd soon know who's who and what's what.--C. Mathews, The Motley Book, p. 13.
for that or who. A vulgarism often heard amongst us, but probably still more common in England. ...
Dictionary of American Words And Phrases by John Russell Bartlett.
In New York a piece of furniture usually placed in a parlor, consisting of several shelves, upon whi...
Dictionary of American Words And Phrases by John Russell Bartlett.