The phrase is sometimes said to have originated with Roman Marcus Junius Brutus during the assassination of Julius Caesar on 15 March 44 BC,   but according to Plutarch, Brutus either did not have a chance to say anything, or if he did, no one heard what was said:
Caesar thus done to death, the senators, although Brutus came forward as if to say something about what had been done, would not wait to hear him, but burst out of doors and fled, thus filling the people with confusion and helpless fear. 
Marcus Junius Brutus was the descendant of Lucius Junius Brutus who was the founder of the Roman Republic and traditionally one of the first consuls in 509 BC. This followed his successful overthrow of the Roman monarchy. Prior to the establishment of the Roman Republic, Rome had been ruled by kings. Brutus led the revolt that overthrew the last king.
The overthrow of the Roman monarchy, a political revolution in ancient Rome, took place around 509 BC and resulted in the expulsion of the last king of Rome, Lucius Tarquinius Superbus, and the establishment of the Roman Republic. The King's son, Sextus Tarquinius, raped a noblewoman, Lucretia. Afterwards she revealed the offence to various Roman noblemen, and then committed suicide. The Roman noblemen, led by Lucius Junius Brutus, obtained the support of the Roman aristocracy and the people to expel the king and his family and to institute a republic.
The phrase has been invoked historically in Europe and other parts of the world as an epithet or rallying cry against abuse of power.
John Wilkes Booth wrote in his diary that he shouted "Sic semper tyrannis" after shooting U.S. President Abraham Lincoln on April 14, 1865, in part because of the association with the assassination of Caesar.    The phrase was also in the pro-Confederate Civil War song " Maryland, My Maryland", which was popular at the time with Southern sympathizers in Maryland, such as Booth. The song, containing the phrase, is now the official state song of Maryland.
The phrase was recommended by George Mason to the Virginia Convention in 1776, as part of the commonwealth's seal. The Seal of the Commonwealth of Virginia shows Virtue, spear in hand, with her foot on the prostrate form of Tyranny, whose crown lies nearby. The Seal was planned by Mason and designed by George Wythe, who signed the United States Declaration of Independence and taught law to Thomas Jefferson.  A joke referencing the image on the seal that dates as far back as the Civil War, is that "Sic semper tyrannis" actually means "Get your foot off my neck." 
"Happy While United" was the slogan on a medal coined by the State of Virginia in 1780. First envisioned by Thomas Jefferson, the medal was minted and designed to be given to Indian signatories to the treaties Jefferson planned with the First Peoples of Virginia. The medal portrays a Virginia colonial sitting enjoying a peace pipe with a Native American. The obverse portrays a variation of the Virginia state seal of the state symbol standing triumphant over a slain enemy with the legend: "Rebellion to Tyrants Is Obedience to God".
Great Seal of Virginia with the commonwealth's motto.
- Mitgang, Herbert (12 April 1992). "Booth Speech Reveals a Killer's Mind". The New York Times. Retrieved 23 November 2015.
- Mulvihill, Amy (13 April 2015). "The Fault in His Stars". Baltimore Magazine. Retrieved 23 November 2015.
- Plutarch, "Caesar", Plutarch's Lives, with an English Translation by Bernadotte Perrin. Cambridge, MA. Harvard University Press. London. William Heinemann Ltd. 1919. ch. 67. On Line text.
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- "Diary Entry of John Wilkes Booth". umkc.edu. Archived from the original on 2010-12-29.
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- Kilzer, Lou; Flynn, Kevin (1997-12-19). "Did McVeigh Plan to get Caught, or was he Sloppy?". Denver Rocky Mountain News.
- Rowland, Kate Mason (1892). The Life of George Mason, 1725-1792. G.P. Putnam's Sons. pp. 264–265.
von Borcke, Heros (April 1866).
"Memoirs of the Confederate War for Independence".
Blackwood's Edinburgh Magazine. American edition, vol. 62. New York: Leonard Scott & Co. 99 (606): 462. Retrieved 21 August 2010.
...the coat of arms of the state of Virginia, bearing the motto, Sic semper tyrannis, which the soldiers translated, "Take your foot off my neck", from the action of the principal figure ... representing Liberty, who, with a lance in her right hand, is standing over the conquered and prostrate tyrant, and apparently trampling on him with her heel.
- Webster entry - audio pronunciation