plant of the genus papaver, having showy flowers and milky juice with narcotic properties, from late Old English popig, popæg, from West Germanic *papua-, probably from Vulgar Latin *papavum, from Latin papaver "poppy," perhaps a reduplicated form of imitative root *pap- "to swell."
Associated with battlefields and war dead at least since Waterloo (1815), an association cemented by John McCrae's World War I poem, they do not typically grow well in the soil of Flanders but were said to have been noticeably abundant on the mass graves of the fallen French after 1815, no doubt nourished by the nutriments below. Poppy-seed is from early 15c.; in 17c. it also was a small unit of length (less than one-twelfth of an inch).
1840, "exaggerated, blind nationalism; patriotism degenerated into a vice," from French chauvinisme (1839), from the character Nicholas Chauvin, soldier of Napoleon's Grand Armee, who idolized Napoleon and the Empire long after it was history, in the Cogniards' popular 1831 vaudeville "La Cocarde Tricolore." The meaning was extended to "excessive belief in the superiority of one's race" in late 19c. in communist jargon, and to (male) "sexism" in late 1960s via male chauvinist (q.v.).
The surname is a French form of Latin Calvinus and thus Calvinism and chauvinism are, etymologically, twins. The name was a common one in Napoleon's army, and if there was a real person at the base of the character in the play, he has not been certainly identified by etymologists, though memoirs of Waterloo (one published in Paris in 1822) mention "one of our principal piqueurs, named Chauvin, who had returned with Napoleon from Elba," which action implies the sort of loyalty displayed by the theatrical character.