The Dactyliomancist

“I once knew a girl who was a dactyliomancist,” said Willie Garvin. He sat on a high stool in the big kitchen of the penthouse, eating raisins from a jar at his elbow.
“A what?”
“A dactyliomancist. This girl I knew.”
She gave a casual nod. “Oh, was she?”
“M’mm.” Willie ate some more raisins. “She used a ring about two inches across, made of iron, with a little ’ole on one edge and a spike opposite.”
(The Silver Mistress, chapter 4)