boom

The Dutch word boom means tree or beam — cognate with German Baum and English beam. Dutch sailors used boom to describe the long horizontal spar at the bottom of a fore-and-aft sail. The boom swings side to side as the wind shifts, and if you fail to duck when it crosses the deck, it will knock you overboard. The phrase 'lower the boom' comes directly from this hazard.

English borrowed the nautical boom by the 1660s. But the word's journey from tree to spar was only the beginning. By the 1700s, boom also meant a barrier of chained logs stretched across a river to block enemy ships — because these barriers were literally booms, tree trunks floating in the water. The boom across the River Shannon during the Siege of Limerick in 1690 was one of the most famous.

The explosive boom — the sound — has a different origin, probably onomatopoeic, first recorded in the 1400s. But English speakers conflated the two. An economic boom, first used in the 1870s during American railroad expansion, may have drawn from both the sound of dynamite blasting through mountains and the sudden extension of something outward, like a sail boom catching wind.

A single syllable now covers tree trunks, sail spars, river barriers, explosions, microphone poles, and economic surges. Dutch gave English a word for wood, and English turned it into a word for everything that extends, blocks, or erupts.