jQuery
The dollar function that made a generation of web pages click.
In 2006 John Resig released jQuery. For a decade the web used its dollar function to find and change a page.
John Resig, 2006
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In 2006 John Resig released jQuery and showed it at BarCamp in New York, to a room of people tired of writing a different DOM call for every browser. Its dollar function became the way a generation reached into a page.
The bars are the opening of that dollar function. Give it a function and it waits for the document; give it a selector, a node, or another jQuery object and it takes that other path. Every method hands the wrapper back, so calls chain.