Q From David Halperin, Israel: Why the tinker in a tinker’s damn?
A There are two theories about this one. One points to the very low social status of tinkers, itinerant menders of pots and pans, and to their well-known tendency to include a swearword in every sentence. So to say that something “isn’t worth a tinker’s damn” is to say that it’s of no value at all, not worth even a moment’s consideration.
A more ingenious explanation was put forward in the latter part of the nineteenth century: when a tinker was soldering a pot, he would make a small wall out of bread dough around the place he was to flood with solder in order to stop it from spreading. After he had finished, he would naturally throw the dough away as being of no further use, so that “a tinker’s dam” was equally something of no value.
A century ago, the compilers of the First Edition of the Oxford English Dictionary were scornful of this attempt to make a simple matter more complicated, though it is still to be found in current works on phrase histories. It speaks to that part of us that wants to convert the mundane to the magical, to find something of mystery and interest in even the most ordinary of expressions.
You may gather that I consider the simpler story to be much the more likely. It is supported by variations such as tinker’s curse and tinker’s cuss.