the.com/yank

means To pull or jerk something suddenly and sharply, or, capitalized, an informal name for a person from the United States (especially used by non-Americans or, in the US Civil War context, a Northerner).

from The two words really did arrive separately. 'Yank' meaning a sharp pull shows up in the 1800s, likely from dialect in the British Isles, though its exact roots are murky — nobody's traced it to a tidy single source. 'Yankee' is older, from colonial-era America, probably rooted in a Dutch nickname (possibly 'Janke,' a diminutive of 'Jan,' or a Dutch jab at English settlers) that got pinned on New Englanders, then Americans generally. 'Yank' as shorthand for 'Yankee' only got clipped down later. Two unrelated words, same sound, one happy accident of English.