No one invented it,it was dicovered* and first used in the 14 hundreds.

According to D. E. Smith, _History of Mathematics_, the sign
originated in 15th-century manuscripts as

o o
per c or p c

for “per cento” or “per hundred.” By the mid-17th century it was

o
per —-
o

and later the “per” was dropped. Later it was tilted into what Smith
calls the “solidus form, %”, since “/” is called a solidus.

I seem to recall somewhere reading that it was originally “numero per
cento” in Italian, which was written as

o /
n / c

using the solidus for “per,” as in a fraction; the c closed up to form
a second o, while the n disappeared. I can’t think what book that could be from, if not from Smith; but Smith apparently doesn’t agree.So this may just be a figment of my imagination.

- Doctor Peterson, The Math Forum