The term ‘mast’ comes from the ancient English word ‘mæst’ and traditionally means the fruit of beech, oak, chestnut and other forest trees, especially as food for pigs. In mast years, pig herders would fatten their pigs on the glut of acorns and nuts.
Illustration from Luttrell Psalters (c. 1325–1340) copyrighted inside the UK, © British Library.