pelting-irons, n. — Green’s Dictionary of Slang

pelting-irons n.

[SE pelt, to throw hard, i.e. the aggressive image of intercourse]

the testicles.

1660		Mercurius Fumigosus 1 6: One of the Watermens Breeches being torn behind, his Pelting-Irons hanging out a great Salmon taking them for Bait, leapt at them.
1661		Mercurius Democritus 22 May 6: If this be the scowring Irons to invirone my pelting-Irons with your Water-mill, you shall scowre no more for me.