shawm n.

medieval oboe-like instrument, late 14c., shalemyes (plural), also schallemele, from Old French chalemie, chalemel, from Late Latin calamellus, literally "a small reed," diminutive of Latin calamus "reed," from Greek kalamos "reed, grass-stalk," often metaphoric of objects made of reed ("flute of reed, fishing rod, reed pen," etc.).

The Greek word is from PIE *kole-mo- "grass, reed," source also of Old English healm, Old High German halm "straw;" Latin culmus "stalk;" Old Prussian salme "straw," Latvian salms; Russian soloma. Sanskrit kalama- "writing reed," Arabic qalam are said by Beekes to have been borrowed from the Greek word.

Mistaken as a plural and trimmed of its "-s" ending from mid-15c.  Perhaps also influenced along the way by Old French muse as the name of a wind instrument (as in the Middle English variant shalmuse). Related: Shawmist. Shawm also was used as a verb c. 1500, of ducks, "to honk" (make a noise like a shawm).