Green’s Dictionary of Slang

mompyns n.

also munpins
[lit. ‘mouth-pins’]

the teeth.

[UK]Towneley Mysteries ‘Prima Pastorum’ (3) line 209: Let vs go foder Oure mompyns .
[UK]Lydgate Minor Poems 30: Thy mone-pynnes bene lyche old yuory Here are stumpes feble and her are none .
[UK]Skelton ‘How the Douty Duke of Albany’ in Henderson Complete Poems (1948) 406: I shrewe thy Scottishe lugges, Thy munpynnys, and thy crag.