jumper

Jumper comes from jump ("short coat"), originally sailors' jargon, plus the agent suffix -er. Jump itself is possibly from Scottish English jupe ("man's loose jacket or tunic"), traced through Middle English juype/gype/joupe and Old French jupe/juppe back to Arabic جُبَّة (jubba); its origin is otherwise uncertain.

The word began as sailors' slang for a short coat before the -er suffix was added to form jumper, the garment name used today.

It's cognate with Middle Low German jōpe/gōpe and German Joppe, both meaning waistcoat or jacket — distant cousins from the same garment-word family.