A person or creature that gallybags; one who wanders aimlessly or causes mischief.
From 'gallybag' (to wander or go about aimlessly) plus the agent suffix '-er'; primarily dialectal Irish and British English.
Words ending in '-bagger' often describe people who do something characteristically—like 'swagbagger'—and this one captures the Irish verbal tradition of turning any action into a character type with playful naming.
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