The piano is my forte

Today is the 152nd anniversary of Chopin's death, an appropriate day to look at the word "piano".  When pianos were first invented, around the beginning of the 1700s, the available keyboard instruments were the clavichord, which was very expressive but had the disadvantage that, well, you couldn't really hear it, and the harpsichord, which you could hear, but it had no mechanism for playing quieter or louder; the harpsichord had two volume levels: on or off.
Around 1700, one Bartolomeo Cristofori, who worked at the Medici court in Florence, invented a new instrument which created sound by a hammer striking a wire (whereas the harpsichord depends on a plucking mechanism). Because the volume could be varied by how hard the hammer hit, this new instrument was called a gravicembalo col piano e forte (‘harpsichord with soft and loud’). Not surprisingly, this got shortened to "piano e forte", then to "pianoforte" and within 70 years of its birth, to "piano".  No doubt Cristofori would have spluttered, "But, but, it plays forte TOO! That's the whole point!!"
The Italian musical terms piano (soft) and forte (loud) established themselves in English at about the same time. Piano literally means "plane" or "flat". It comes from the Latin word planus. Because the flat areas in Italy are in the lower coastal parts of the country, the word also came to mean "low", first in reference to height and then in reference to sound. Forte literally means "strong".
And here's my favourite bit of Chopin (both piano and forte) to enrich your day (starting at 0:30):