Piano is Italian, shortened from pianoforte, which means "soft-loud" — the instrument was named for what it could do that a harpsichord could not, namely play at different volumes depending on how hard you hit the key. English took the short form in 1803 through French.
The word itself is a good specimen of the Italian musical layer in English: piano, opera, soprano, tempo, crescendo, sonata, concerto, all borrowed wholesale because Italy set the terms of the art. The -o ending is the visible marker. Behind the Italian piano, "soft," is Latin planus, "flat, smooth, level" — the same word that gives English plain and plane. The musical direction piano, meaning softly, entered English separately in the 1680s, more than a century before the instrument did.
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. also from 1803 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"). also from 1680s
piano came in through Later and wider borrowings, and its spelling follows that family's conventions.
How that family writes these sounds
| an unstressed vowel ending a word about food or music | Italian or Spanish: -o, -a, -ipiano, opera, spaghetti, tornado |
What gives it away on the page
| -o/-a/-i endings, gh for hard g, cc | Italian — music, food, and architecture.piano, opera, graffiti, spaghetti, ghetto, broccoli, balcony |
Placing it without the spelling
| music, food, and architecture from Italy | Italianpiano, opera, spaghetti, ghetto |
| an unstressed vowel on the end, in food, music, or weather | Italian or Spanishpiano, opera, tornado, cargo |
Later and wider borrowings in the spelling guide · guess another word's family