Up to snuff
Initially, the phrase meant 'sharp and in the know'; more recently, 'up to the required standard'.
'Up to snuff' originated in the early 19th century. In 1811, the English playwright John Poole wrote Hamlet Travestie, a parody of Shakespeare, in the style of Doctor Johnson and George Steevens, which included the expression.
"He knows well enough The game we're after: Zooks, he's up to snuff." &
"He is up to snuff, i.e. he is the knowing one."
A slightly later citation of the phrase, in Grose's Dictionary, 1823, lists it as 'up to snuff and a pinch above it', and defines the term as 'flash'. This clearly shows the derivation to be from 'snuff', the powdered tobacco that had become fashionable to inhale in the late 17th century. The phrase derives from the stimulating effect of taking snuff. The association of the phrase with sharpness of mind was enhanced by the fashionability and high cost of snuff and by the elaborate decorative boxes that it was kept in.
The later meaning of 'up to standard', in the same sense as 'up to scratch' (see also: 'start from scratch') began to be used around the turn of the 20th century.