They knew about percentages (and actively used them as a kind of calculation system) back in the ancient Roman state. Then fractions were used as a definition of the amount of the tax on goods (its value was one hundredth).
Percentage Calculator https://percent-calc.com/ A simple way to calculate percentages of X.
According to numerous sources, such a fractional system was actively used later, already in the Middle Ages. It was used to calculate the amount of interest rates, as well as the amount of income and losses. Since the 17th century, this system has become the general standard for such calculus.
The mathematical sign of the percentage and the history of its origin
How did this mathematical sign, which stands for "percentages" and is known all over the world today, arise? It turns out that the history of its origin is very interesting, and it arose as a result of a simple typo! So, a French mathematician in 1685 published a work called "A Guide to commercial arithmetic".
At the same time, he used the abbreviation "cto"to indicate the percentage. When he gave his manuscript to print, the person who typed his text took this abbreviation as a fraction and printed it in the book exactly like this: "0/0".
That's how this sign was born — as a result of a banal typo of the typesetter! And very quickly it became popular and recognizable all over the planet.