"dried berries of the pepper plant," Middle English peper, from Old English pipor, from an early West Germanic borrowing of Latin piper "pepper," from Greek piperi, probably (via Persian) from Middle Indic pippari, from Sanskrit pippali "long pepper." The Latin word is the source of German Pfeffer, Italian pepe, French poivre, Old Church Slavonic pipru, Lithuanian pipiras, Old Irish piobhar, Welsh pybyr, etc.
Application to fruits of the Capsicum family (unrelated, originally native of tropical America) is from 16c. To have pepper in the nose in Middle English was "to be supercilious or unapproachable."
"grain," Old English corn "single seed of a cereal plant; seeds of cereal plants generally; plants which produce corn when growing in the field," from Proto-Germanic *kurnam "small seed" (source also of Old Frisian and Old Saxon korn "grain," Middle Dutch coren, German Korn, Old Norse korn, Gothic kaurn), from PIE root *gre-no- "grain."
The sense of the Old English word was "grain with the seed still in" (as in barleycorn) rather than a particular plant. Locally understood to denote the leading crop of a district. It has been restricted to the indigenous "maize" in America (c. 1600, originally Indian corn, but the adjective was dropped), usually "wheat" in England, "oats" in Scotland and Ireland, while Korn means "rye" in parts of Germany.
Maize was introduced to China by 1550, it thrived where rice did not grow well and was a significant factor in the 18th century population boom there. Corn-starch is from 1850. Corn-silk is attested from 1852.
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Definitions of peppercorn from WordNet
pungent seasoning from the berry of the common pepper plant of East India; use whole or ground;