Accordion
mid 19th century: from German Akkordion, from Italian accordare ‘to tune’.
wiktionary
First attested in 1831. From German Akkordeon, from Akkord(“harmony”), from French accord, from Old French acorder, based on Italian accordare(“to tune”). See also accord.
etymonline
accordion (n.)
"small, keyed, bellows-like wind instrument," 1830, from German Akkordion, from Akkord "musical chord, concord of sounds," from a verb similar to Old French acorder "agree, be in harmony," from Vulgar Latin *accordare (compare Italian accordare "to attune a musical instrument;" see accord (v.)), with suffix on analogy of clarion, etc. Invented 1829 by piano-maker Cyrill Demian of Vienna. The type with a keyboard instead of buttons is a piano accordion. Related: Accordionist.
