Everyone familiar with American politics knows about the “bloody shirt” — that durable symbol of martyrdom and outrage guaranteed to stir up the masses, or at least the party faithful, at election time. The left’s recent seizure of the Giffords shooting as an opportunity to bash the right was only the latest instance of bloody-shirt-waving.

But was there a particular garment that gave rise to the metaphor? Search the Internet using the terms “’bloody shirt’ + American politics” and you’ll get page upon page of results, most discussing the meaning of the term itself, contemporary usages, and historical incidents reaching back to the assassination of Julius Caesar. There is also reference to a speech by Benjamin Butler in the House in 1871 in which he told of a horrific incident in Mississippi in support of an anti-terrorism bill aimed at the South. But although white southerners accused Butler of “waving the bloody shirt” in order to further oppress them, Butler did not, in fact, wave a shirt or anything else (except, perhaps, his hands) during his speech.

It must be acknowledged that there was more than one famous bloody shirt in those days. When Charles Sumner of Massachusetts was brutally caned by Preston Brooks of South Carolina on the floor of the Senate in 1856, Sumner’s beating became a symbol of what abolitionists saw as the “Slaveocracy’s” depravity — and southerners charged that he later used his red-stained clothes to stir up sympathy. Northern partisans were also quick to decry incidents after the war, when northerners who went south to administer Reconstruction were sometimes flogged or otherwise assaulted by southerners accusing them of “carpet-bagging.”

Nevertheless, a strong argument can be made that there was a bloody shirt — the uniform tunic worn by the young Col. Elmer E. Ellsworth on the morning of his shocking death on May 24, 1861.

Ellsworth, a Union colonel of volunteers and close friend of Abraham Lincoln, had just seized a large rebel flag from the top of the Marshall House, an inn in Alexandria, Va. The inn’s owner, James Jackson, met Ellsworth as he was coming down the stairs from the roof, holding the flag that Jackson had hoisted as an insult to Lincoln, who could see it from the White House. Jackson was holding something, too: a loaded shotgun. He blasted Ellsworth in the chest at point-blank range. Jackson was killed in turn by a soldier.