If you are like me and I suspect most English speakers you spelt it “Peso” you have been spelling it wrong.
It became Peso the Piso in 1967 if you on Philippines note or coins you will see it says Piso. It is rumoured that it became Peso under American rule as they used the English spelling, however that is not correct.
In Spanish the word “peso” means weight and was the name given to the 8-royal coin or real de a ocho which had a legal weight of 27.468 grams. So the Filipino Piso was probably spelt “Peso” a long time before English was introduced to the Philippines.
Piso is the Tagalog spelling of Peso. After a lot of research into how the Spanish word Peso changed its spelling in Tagalog and after asking many locals I am still none the wiser, as it seems the locals do not know why the spelling got changed. If you know why this happened please comment below.
With immediate effect, the following change is made to
“List one: Currency, fund and precious metal codes”:
Amended currency name for PHILIPPINES (THE): Philippine Piso (instead of Peso)
So that is the reason you now see it spelt “Philippines Piso” when you use XE Currency Converter, OANDA or any of the other Foreign Exchange Rates converters.