Wig

Soured milk or buttermilk, sometimes flavoured with herbs, as a drink, known from 1528 until the 19th century (OED).

This may be the drink prepared in medieval monasteries under its Latin names of lac acidum for the version prepared from Hokeday to Michaelmas, and lac dulce from Michaelmas to Martinmas (History of The Anglo-Saxons, by Sharon Turner, 1852)