means A rover is a wandering traveler with no fixed destination, or by extension a vehicle built to roam — especially a robotic one exploring distant planetary surfaces.

from From the verb 'rove,' to wander, which likely came into Middle English from Dutch or Low German 'roven,' meaning to rob or plunder — the same restless root that gives us 'rover' in the older sense of a sea-pirate or roaming raider. Over time the menace drained away, leaving just the wandering: from plundering buccaneer to a Mars buggy puttering across the dust. A cousin of this word survives in 'free rover,' and the Boy Scouts' senior 'Rovers' kept the gentler, roaming spirit.