kingpin (n.) Look up kingpin at Dictionary.com
also king-pin, 1801 as the name of the large pin in the game of kayles (similar to bowls except a club or stick was thrown instead of a ball; see "Games, Gaming and Gamesters' Laws," Frederick Brandt, London, 1871), from king with a sense of "chief" + pin (n.). The modern use is mainly figurative and is perhaps from the word's use as another name for the king-bolt (itself from 1825) in a machinery, though the figurative use is attested earlier (1867) than the literal.