Piano
early 19th century: from Italian, abbreviation of pianoforte.
wiktionary
Short form of pianoforte, from Italian pianoforte, from piano(“soft”) + forte(“strong”). So named because it could produce a wide range of varied volumes note-by-note, in contrast to older keyboard instruments, notably the harpsichord. Doublet of llano, plain, and plane.
From Italian piano.
etymonline
piano (n.)
"percussion musical instrument in which tones are produced by blows of hammers upon stretched strings, the hammers being operated from a keyboard," 1803, from French piano (18c.), Italian piano, shortened forms of pianoforte (q.v.).
Essentially, the pianoforte is a large dulcimer with a keyboard ; but historically it replaced the clavichord and harpsichord, which were keyboard-instruments more akin to the harp than to the dulcimer. [Century Dictionary]
Piano wire "kind of strong steel wire used for strings of pianos," is attested from 1831. Piano-case "wooden box enclosing the mechanism of a piano" is by 1844.
piano (adv.)
musical instruction, "softly, with little force or loudness," 1680s, from Italian piano, which is ultimately is from Latin planus "flat, smooth, even," later "soft" (from PIE root *pele- (2) "flat; to spread").
