miller's thumb

Also found in: Wikipedia.

mill·er's thumb

Any of several small freshwater sculpins of the genus Cottus, having a large spiny head and spiny fins, especially the European species C. gobio.

[From its stocky, thumblike shape (the phrase miller's thumb was originally a folk expression referring to millers who gave short weight by tipping the scales with their thumbs).]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

miller's thumb

(Animals) any of several small freshwater European fishes of the genus Cottus, esp C. gobio, having a flattened body: family Cottidae (bullheads, etc)
[C15: from the alleged likeness of the fish's head to a thumb]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in classic literature ?
``Come on, churl, an thou darest: thou shalt feel the strength of a miller's thumb!''
He often would Hurly-burly Get up early And go By hook or crook To the brook, And bring home Miller's Thumb, Tittlebat Not over fat, Minnows small As the stall Of a glove, Not above The size Of a nice Little baby's Little fingers."
WHAT sort of creature is a miller's thumb? WHERE is Holyroodhouse?
This strangely-named fish, which appears to have been very common, was probably the Miller's Thumb, a fish which was still in the river but much rarer in the 1960s.
Miller's Thumb Brewing Company based at the Canal bar and restaurant, brews several great draught beers at its Anniesland micro-brewery but has finally taken the plunge and bottled this stunning golden wheat beer.
The Canal complex is home to the pioneering microbrewery, Miller's Thumb, which aims to spread baby-sized brewing across Britain just as it's taken off in The States.
And he must be telling the truth, because this has turned into something of a lifelong love-affair for Jim, who, at 32, is the master brewer for the new Miller's Thumb restaurant and microbrewery at Anniesland Cross in Glasgow's west end.
Jim starts around 6.30am, brewing one of the six different varieties he produces for Miller's Thumb.
The first Miller's Thumb micro-brewery opens its doors on the flag-waving Fourth of July on Bearsden Road in Glasgow.
A further 100 jobs will be available in the company's flagship Miller's Thumb micro-brewery, which opens in Glasgow's Anniesland this summer.
The chain will trade under the name Miller's Thumb Brewing Company.
and Sienna Miller's thumbs have been taking a real battering.