reed

"tall, broad-leafed grass growing in wet places," Old English hreod "reed, rush," from Proto-Germanic *kreut- "reed" (cf. Old Saxon hraid, Old Frisian hriad, Middle Dutch ried, Dutch riet, Old High German hriot, German Ried), with no known cognates beyond Germanic.

Meaning "musical pipe made from a reed stem" is from late 14c. (reed-pipe is from c.1300). As part of the mouthpiece of a musical instrument it is attested from 1520s. Meaning "a reed instrument" is from 1838.

A thin piece of wood or plastic used in many woodwind instruments. It vibrates when the player holds it in the mouth and blows over it (as with a single reed) or through it (as with a double reed). Clarinets and saxophones use a single reed; bassoons and oboes use a double reed.

A weak or unreliable support, as in I'd counted on her to help, but she turned out to be a broken reed. The idea behind this idiom, first recorded about 1593, was already present in a mid-15th-century translation of a Latin tract, “Trust not nor lean not upon a windy reed.”

see broken reed.