To begin a new task, job, or project immediately, energetically, and effectively, with little or no settling-in time. It suggests readiness, momentum, and a successful start from the first moment.

The exact origin is disputed. The image is literal: landing and immediately running, as with someone jumping from a train, troops landing, riders changing mounts, or later parachutists. Phrase Finder records literal U.S. newspaper use in 1895 and identifies figurative use by 1940; modern dictionaries define it as starting quickly and effectively. The expression likely moved from physical quick starts into business, sport, and everyday speech.