'mast' originates from Old English 'mæst' (also written 'mǣst' or 'mǣst'), from Proto-Germanic '*mastiz', meaning 'food' or 'fodder' (especially tree-fruits used as animal food).

'mast' in Old English referred chiefly to forest fruits (acorns, beech-nuts) used as animal fodder; the word continued into Middle English as 'mast' and retained both the sense of tree-fruits and, by extension in nautical vocabulary, a tall support or spar ('mast'). Over time these senses existed in parallel in modern English as distinct but related meanings.

Initially it meant 'forest fruits used as animal fodder'; over time an additional sense developed referring to a tall pole or spar on a ship, and both senses survive in modern usage.