euphony (n.)

mid-15c., from Middle French euphonie, from Late Latin euphonia, from Greek euphonia "sweetness of voice," related to euphonos "well-sounding," from eu- "good" (see eu-) + phone "sound, voice," from PIE root *bha- (2) "to speak, tell, say." Related: Euphonic (1782); euphonical (1660s); euphonious (1774). Hence, also, euphonium (1864), the musical instrument.