Thumbing through English’s thumb expressions
First, what about the word thumb itself? Incredibly, the Oxford English Dictionary finds evidence for the word – in the form of the Old English þúma – in an Anglo-Latin glossary dated to around 700. With cognates across the Germanic languages, thumb ultimately goes back to an ancient root meaning ‘swell’, making the digit a kind of ‘stout or thick finger’. Its final b, recorded by the late 13th century, is the result of epenthesis. This phonological process adds sounds into words and also gives us the b in limb, humble, nimble, and thimble, whose root is the word thumb.
The OED dates green thumb back to 1937 in an edition of the Michigan-based Ironwood Daily Globe: ‘Besides being green-eyed, Miss Dvorak has what is known as “the green thumb.” That’s horticultural slang for being a successful gardener with instinctive understanding of growing things’.
An earlier version of this expression, found in 1906, is green fingers, and someone who lacks the gardening magic is sometimes referred to as having a brown thumb.
Golden thumb/miller’s thumb
In the Middle Ages, millers were often seen as dishonest, possibly due to a reputation for adulterating their product for greater profits. In the Prologue to his Canterbury Tales, Chaucer writes of a devious miller with a ‘thumb of gold’, leading to the expressions golden thumb and miller’s thumb. According to Mark Allen and John Fisher in their scholarship on Chaucer, the gold ‘implies he kept his thumb on the scales’. The OED notes that the gold may also reference the returns from such an underhanded practice.
A thumb on the scale
To put your thumb on the scale is to manipulate an outcome in your favor by deceptively influencing it, alluding to merchants who would, apparently, press their thumbs down on scales to make a product seem heavier, and thus more expensive, than it really is. The idiom looks to be recent, with Google Books first turning it up A. Q. Mowbray’s The Thumb on the Scale; or, The Supermarket Shell Game, which exposes how packaging and labeling can cheat consumers.
A thumb is typically about an inch in breath and not much longer, so it’s unsurprising English used it for little things, like Tom Thumb, a character of diminutive stature – though of great adventure – in English folklore since at least the early 1500s.
Rule of thumb
It’s often claimed rule of thumb – a ‘practical method’ – originates in an old rule allowing a husband to beat his wife as long as its with an instrument no thicker than his thumb. This explanation is rubbish, though a British judge, Sir Francis Butler, allegedly made such a pronouncement in the 1780s, leading to the popular folk etymology today. Rather, rule of thumb, attested in 1658, more likely comes from the use of body parts for everyday measurements, with rule as ruler. Consider units like the foot, finger, and hand, which is still employed to size up horses today.
Thumb one’s nose
Etymologists thumb their noses at the rule of thumb folk etymology. This expression for showing disdain is also a derisive gesture: placing one’s thumb on the tip of the nose and extending the figures. The gesture, recorded as early as 1854, is also known as cocking a snook, which, though of obscure origin, is found much earlier in 1791.
Bite one’s thumb
Another thumb-based expression is to bite your thumb at someone, an insulting gesture involving flicking your thumbnail from behind the upper teeth, as the Norton Shakespeare explains it. Thumb-biting is memorably featured in Shakespeare’s Romeo and Juliet when Capulet servingman Samson cleverly taunts a Montague: ‘No, sir, I do not bite my thumb at you, sir, but I bite my thumb, sir’. Samson is playing on another sense of to bite one’s thumb, or ‘show anger or frustration’.
Twiddle the thumbs
Thumb a ride
And to thumb a ride, found as early as 1932, is a colloquialism for ‘to hitch-hike’, which, in many places, involves extending the arm towards the road while signaling with the thumb popped up.
Stick out like a sore thumb
A hitchhiker who never lands a lift might complain about a sore thumb, but to stick out like a sore thumb is ‘to be very conspicuous’, as an injured thumb might be cocked away from the rest of the hand, especially if held in place by a bandage. The OED first finds the phrase as stand out like a sore thumb in 1936.
Under the thumb
Mick Jagger has had us under his thumb since 1996, but the expression, meaning ‘to be completely under someone’s control’, is far older, in written use since at least 1753.
And yet older is to be all thumbs, or ‘lacking dexterity’, recorded as ‘each finger is a thumb’ in John Heywood’s 1546 collection of English proverbs.
And finally, here’s a thumbnail sketch of some more obscure or obsolete thumb expressions in the OED:
- To get one’s thumb out of a person’s mouth: to escape from
- The finger next one’s thumb: one’s closest friend
- To be finger and thumb: to be on intimate terms
- To a cow’s thumb: exactly, perfectly, to a hair
- There’s my thumb: a solemn declaration, in allusion to the practice of licking the thumb in sealing a bargain
- Above one’s thumb: beyond one’s reach or ability
- To keep the thumb on: to keep secret