The phrase all aboard became standard in the age of steam rail travel, called out by conductors to warn passengers that a train was about to depart. The same call was later adopted on ships, buses and in countless cartoons and films, turning it into a universally understood signal to leave. Online, the short shouted version survives as a reusable departure cue, clipped for memes, travel edits and group chat jokes whenever someone announces they are heading out or dragging everyone along on a trip together.