In Cockney rhyming slang, ‘mince pies’ means eyes. The phrase works in the usual way: ‘pies’ rhymes with ‘eyes’, and the whole term stands in for the word it echoes. In everyday speech it is very often cut down to just ‘minces’, so someone might be said to have lovely minces, meaning their eyes. Green’s Dictionary of Slang defines the term plainly as ‘an eye’, usually used in the plural, which matches how it tends to be used: almost always about a pair of eyes rather than a single one.
What’s the origin of the phrase ‘mince pies’?
Rhyming slang of this kind is generally dated by historians to the East End of London in the early nineteenth century. ‘Mince pies’ for eyes belongs to this tradition, and the pairing has been in use since at least the mid-1800s, making it one of the older and more firmly established examples of the form.
The first substantial published record of Cockney rhyming slang appeared in 1857, in a glossary compiled by the lexicographer writing under the name Ducange Anglicus. Collections of this sort are how a great deal of the slang from this period survives at all, since it was mostly spoken rather than written down, and ‘mince pies’ sits among the terms that were current by the time such glossaries began to appear.
The mechanics of the phrase follow the standard pattern for rhyming slang: a phrase is chosen because its final word rhymes with the word actually meant, and then, once the phrase is familiar enough, the rhyming word itself can simply be dropped. That is what happened here, with ‘mince pies’ shortened to ‘mince’, commonly pluralised as ‘minces’, so that the food reference all but disappears from the everyday form even though everyone using it still means eyes.