Pea
mid 17th century: back-formation from pease (interpreted as plural).
wiktionary
Back-formation from pease, an original singular reinterpreted as a plural. Further from Middle English pese(“a pea”), from Old English pisa, from Latin pisa, pisum, from Ancient Greek πίσον(píson).
From having the appearance of a pea (see English etymology 1), the edible seed of Pisum sativum, the pea plant.
From Middle English pe, po, poue, pa, paue, from Old English pēa, pāwa(“peacock”) (compare Old English pāwe(“peahen”)) and Old Norse pái(“peacock”), both from Proto-Germanic *pāwô(“peacock”), from Latin pāvō(“peacock”). Cognate with Saterland Frisian Pau, West Frisian pau, Dutch pauw, German Pfau. Doublet of Pavo.
pea (plural peas)
etymonline
pea (n.)
"the seed of a hardy leguminous vine," a well-known article of food, early or mid-17c., a false singular from Middle English pease (plural pesen), which was both single and collective (as wheat, corn) but the "s" sound was mistaken for the plural inflection. From Old English pise (West Saxon), piose (Mercian) "pea," from Late Latin pisa, variant of Latin pisum "pea," probably a loan-word from Greek pison "the pea," a word of unknown origin (Klein suggests it is from Thracian or Phrygian).
In Southern U.S. and the Caribbean, used of other legumes as well. Pea soup "soup made from peas" is recorded by 1711 (as pease-soup); the term was applied to London fogs at least since 1849. Pea-green as a hue resembling fresh peas is by 1752. Pea-shooter "toy consisting of a long straw or tube through which dried peas may be blown" is attested from 1803.
