Photo by Clément Bucco-Lechat
You don't see so many thimbles about nowadays. In fact they've got so rare that round here the party game Spot the Thimble has been superseded by Spot the Smartie (a Smartie is a small smoothed-edged disc of confectionery made of chocolate with a coloured sugar coating. Yes, that's right, very like an M&M).
Still, if we're unlikely to see a thimble on someone's finger, and not any more likely to see the sort of thimble that's part of the rigging of a sailing boat:
(the thimble is the bit of metal inside the loop)
then a thimble of whisky or some other drink is quite easy (it doesn't literally have to be the amount that'd fit in a thimble, the meaning here is simply a small amount).
We also have thimblerig, which is a game where an object is hidden under one of three thimbles, which are then all moved rapidly about, the point of the game for the observer being to keep an eye on the object-hiding thimble, and for the thimblerigger to cheat so that the watching person guesses which one it is wrongly.
The game of thimblerig is so often crooked that thimblerigger has now extended its meaning to cover a cheat at anything.
Lastly there's thimblewit, a lovely word which I plan to adopt. In the USA this is a person whose wits would apparently fit, yes, in a thimble.
Which makes it a nice easy thing to spot, doesn't it.
Spot the Frippet: thimble. This word comes from the Old English thȳmel, thumbstall, from thūma, thumb.