Slap means makeup used by actors because it is slapped on and jab means an injection. Is there a name for this? It is not the part but the procedure so synecdoche doesn’t work. There must be loads more of these but the only other one I can think of is the crude ‘poke’ which is a verb and a noun unlike slap and jab.

Metonymy

Thanks, Dr. T, for your terse response. Fits the bill.  It reminded me of a section in Postmodernism For Beginners (Icon Books) which I looked up: “Fifty keels ploughed the deeps” illustrating synecdoche, metaphor and metonomy (and mnemonic).  I’d’ve said ‘deep’ not ‘deeps’.

A mnemonic for what?  The trouble with mnemonics is that I can remember the mnemonic long after I’ve forgotten what it’s supposed to remind me of.