The word "Yankee" likely derives from the Dutch name "Janke," a diminutive of "Jan" (John), used as a nickname for Dutch settlers in colonial America. One theory suggests it came from the Dutch phrase "Jan Kees" (John Cornelius), a common name among Dutch settlers, which English speakers mocked. Another theory links it to the Cherokee term "eankke," meaning "coward," possibly applied to New Englanders but the evidence is flimsy at best and given the resilient and bold nature of our Yankee ancestors, unlikely.

Although the exact origin and time is debated, by 1758 during the French and Indian War, British soldiers (often with a derogatory tone) were using it to refer to New Englanders, in particular the militias fighting along side them.

The earliest documented use of "Yankee" appears in the mid-18th century, during the French and Indian War. British soldiers and colonial militias fought together, but cultural differences often led to friction. British troops reportedly used "Yankee" to describe New England militia, possibly as a slight, mocking their provincial manners or Dutch-influenced culture. A 1758 letter from British General James Wolfe to Sir Jeffery Amherst reads

"I can afford you two companies of Yankees, and the more, because they are better for ranging and scouting than either work or vigilance."

It is one of the first written instances and the lack of context added by the author suggests the word was already in common usage. By the 1760s, the term gained traction in colonial America, often carrying a derogatory connotation when used by British loyalists or soldiers. However, during the American Revolution, colonists began to reclaim the term. The song "Yankee Doodle," originally a British satire of American soldiers, was adopted by Patriots as a defiant anthem.

In the immediate after math of the Revolutionary war the term Yankee was relegated to mostly residents of Connecticut and Massachusetts, "Yankee" being sometimes used pejoratively by other Americans, particularly in the Mid-Atlantic and Southern states, to describe New Englanders as shrewd, cunning, or overly frugal. The "Yankee peddler," a stock character in early American folklore, emerged during this period, depicting a sly New England merchant traveling the countryside selling goods (often of questionable quality, like wooden nutmegs). By the early and mid 1800s as the country began to split economically and ideologically, the term began to encompass northerners in general, now seen as a monolith in their opposition to southern and midwestern states.
Yankee became a catch all phrase for Union troops in the southern war regardless of where they came from. After the Civil War, "Yankee" began to transcend its regional connotations, becoming a term for Americans as a whole, particularly in international contexts.
Rudyard Kipling’s writings in the 1890s use "Yankee" to describe Americans broadly, often with a mix of admiration and critique.
In other regions, particularly Latin America during the Spanish American war, "Yankee" acquired negative connotations, symbolizing American imperialism or economic exploitation.

As the American empire grew the Yankee gained a fierce reputation. By WW1 the once degrading term for a rag tag militia struck fear and awe in enemies and allies alike, George M. Cohans famous 1917 song "Over There" proclaimed on radio waves across the world:

"Over there, over there,
Send the word, send the word over there—
That the Yanks are coming,
The Yanks are coming,
The drums rum-tumming
Ev’rywhere.
So prepare, say a pray’r,
Send the word, send the word to beware.
We’ll be over, we’re coming over,
And we won’t come back till it’s over
Over there."
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Americas 26th Infantry Division or the "Yankee Division" saw extremely heavy combat in both WW1 and WW2 as well as guarding the north eastern United States until being gradually decommissioned post Cold War, but not before serving piecemeal in the GWOT, adding to the ever growing, both famous and infamous legacy of the Yankee.