Not worth a tinker’s damn is a phrase that is often uttered, although most people who say it nowadays have no idea what a tinker is. There is also considerable confusion over the word damn in this phrase, which is often misspelled dam.
A tinker was an itinerant tradesman who mended pots and pans. The variant tinkler, common in Scotland, the north of England, and Ireland, appears as an English word in a Latin manuscript, Carta Willelmi Regis, from c.1175.
Que iacet inter terram serlon incisoris et terram Jacobi tinkler.
(Which lies between the land of Serlo the engraver and the land of James the tinkler.)
The name Editha le Tynekere appears in a manuscript from c.1265 (interesting that this is a reference to a tradewoman) and Tomkyn þe Tinkere is a character in William Langland’s 1362 Piers Plowman (A text).
The etymology of tinker is not known for certain. One suggestion is that it is echoic, from either the sound of a bell that the tinker rang to announce he was in the neighborhood (perhaps the name Tinkerbell from Peter Pan is an allusion to this belief) or from the tinking sound a tinker made as he worked on the pots and pans. Another is that it is from the verb to tink, meaning to work in metal. Both are problematic as tinker and tinkler predate any known appearance of tink or tinkle in the sense of a bell or metallic sound or the verb to tink. It is more likely that these come from tinker, not the other way around.
A third suggestion is that it comes from the word tin, the material with which the tinker worked. But there is no strong evidence to support this other than a similarity of form and a logical semantic connection.
As to the phrase tinker’s damn, a variant form appears as early as 1824 in John MacTaggart’s The Scottish Gallovidian Encyclopedia:
A tinkler’s curse she did na care What she did think or say.
The more familiar form is in Henry Thoreau’s Journal of 25 April 1839:
‘Tis true they are not worth a “tinker’s damn.”
Tinkers evidently had a reputation for cursing, like many tradesmen of that or any era, and a tinker’s damn was not worth much because tinkers damned everything.
Some bowdlerize the term and spell it tinker’s dam, citing elaborate and unlikely explanations as to why it should be spelled this way. Evidently they are fond of the phrase but too squeamish to use a scandalous word like damn. The first and most complicated of these explanations makes its appearance in Edward Knight’s 1877 The Practical Dictionary of Mechanics:
Tinker’s-dam, a wall of dough raised around a place which a plumber desires to flood with a coat of solder. The material can be but once used; being consequently thrown away as worthless, it has passed into a proverb, usually involving the wrong spelling of the otherwise innocent word “dam.”
Another explanation is that the dam refers to the tinker’s horse, a female horse being known by that word. This explanation is utterly false. Not only is there no known connection to horses in the history of the term, but dam does not mean female horse; it means mother. A horse has a sire and a dam—a father and a mother.
It’s clear from the early appearance of tinkler’s curse, that the damn in question is a four-letter word.
(Source: Oxford English Dictionary, 2nd Edition)
Copyright 1997-2015, by David Wilton