or tinker's dam
the least value or merit; nothing or anything at all: It's not worth a tinker's damn.
care/give a tinker's damn, to have or feel little or no concern; be unaffected or unmoved: I don't care a tinker's damn for their opinions.
Origin of tinker's damn
First recorded in 1830–40; from tinkers' alleged habit of cursing frequently (hence weakening the force of a curse)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
slang the slightest heed (esp in the phrase not give a tinker's damn or cuss)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012