jumper (n.) Look up jumper at Dictionary.com
1610s, "one who jumps," agent noun from jump (v.). The word meaning "sleeveless dress" (1853) apparently is from mid-17c. jump "short coat," also "woman's under bodice," of uncertain origin, perhaps from French jupe "skirt" (see jupe). Meaning "sleeveless dress worn over a blouse" first recorded American English 1939.