flash

The origin of the word flash is uncertain, although it rhymes with a number of other verbs that also mean forceful, often violent movement that may come to a quick end: dash, lash, crash, slash, clash, gash, bash, splash, smash. These words turn up in English over a fairly long period of time, from dash— the only word in the group with a likely foreign source—in the 14th century, to smash in the 18th century. The element -ash has thus provided a kind of model for new words. The initial fl – that is added to -ash to make flash is also heard in words meaning quick movement, as flee, fly, flicker, and flutter.