The story
From bong + cloud (of marijuana smoke from the bong); exact origin for name uncertain, though perhaps the handle of an online chess player who frequently used this opening technique.
Etymology from Wiktionary, CC BY-SA 4.0.
bongcloud
Today it means: A chess opening in which white's king is advanced to the second rank on the second move, for example, 1.e4 e5 2.Ke2, thus preventing white from being able to castle and allowing black to develop with tempo. Full definition →