The fruit of the oaktree, consisting of a smooth oval nut in a rough cup-shaped base.
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GermanicOld Englishwell-attested
From Old English 'æcern' (nut, mast — the fruit of any forest tree), from Proto-Germanic *akraną (fruit of the field, nut), from PIE *h₂eǵ- (field, open land) combined with a suffix *-no- forming a noun of product. The Proto-Germanic form originally meant 'fruit of the open land' or 'field-fruit,' and applied to nuts and mast of all kinds, not just oak nuts. The modern spelling was reshaped by folketymology
to suggest 'oak' + 'corn' (grain), but neither element is historically present — the word has no etymological connection to oaks specifically, nor to corn. The
in Middle English as the folk etymology took hold and speakers reinterpreted the word through the lens of the dominant nut-bearing tree in English forests. Key roots: *h₂eǵ-ro- (Proto-Indo-European: "field, open land").