Mull over

From the 1850s onward ‘mull’ began to be used in the USA to mean “To allow a problem to be resolved by inaction; to let something ‘stew’.”. It is clear that ‘mull over’ is just an extension of that usage. An early use of the expression in print is found in the February 1874 edition of The Atlantic Monthly:

The stage proprietor, the stage driver, and the hostler, mull over the problem, and sit down on the woman’s hair-trunk in front of the tavern to reason with her.

To know how ‘mull’ came to be used that way it would help to look at the various meanings that mull had prior to 1874. The contenders are:

– Something reduced to dust, ashes, mould, rubbish. – Caxton’s Myrrour of Worlde, 1481″…skrapeth so longe in the duste and mulle til he fynde a gemme.”

– The Scottish term for a promontory or headland. – Bain’s Caledonian Documents, 1307 “Le Moel de Kentyr.” [The Mull of Kintyre]

– The lips or muzzle of an animal – Freiris Berwik, 1568 “Thir mvllis of ȝouris ar callit to ane feist.”

– A cow – Phillips’s Satyr against Hypocrites, 1655 – “To keep the Sabbath such have been our cares, That Cisly durst not milk the gentle Mulls.”

– A plain, thin muslin fabric – Jane Austen, Northanger Abbey, 1817 “The texture of their muslin… the spotted, the sprigged, the mull or the jackonet.”

– A snuffbox – Smollett’s Humphry Clinker, 1771 “The lieutenant pulled out, instead of his own Scotch mull, a very fine gold snuff box.”

– A muddle or mess – Egan’s Life in London, 1821 “Somebody must make a mull – but Randall’s the man.”

It may be that the new meaning of mull was coined independently of the earlier ones. It is more likely though that ‘mull over’ was an allusion to the last on the above list and referred to something being ‘stewed’ in one’s mind.