euphony (n.) Look up euphony at Dictionary.com
mid-15c., from Middle French euphonie, from Late Latin euphonia, from Greek euphonia "sweetness of voice," from euphonos "well-sounding," from eu- "good" (see eu-) + phone "sound, voice," related to phanai "speak" (see fame (n.)).

Hence, euphonium (1865), the musical instrument. Related: Euphonic; euphonious.