The wikipedia entry of gematria starts by stating the following:
Gematria [...] is an Assyro-Babylonian-Greek system of code and numerology later adopted into Jewish culture that assigns numerical value to a word or phrase[...]
This statement was somewhat shocking to me, given the fact that I always believed this practice was of completely jewish origin.
Wikipedia supports this claims with the following information:
Although the term is Hebrew, it most likely derives from Greek geōmetriā, "geometry", which was used as a translation of gēmaṭriyā, though some scholars believe it to derive from Greek grammateia.
The first attested use of gematria occurs in an inscription of Assyrian ruler Sargon II (727–705 BC) stating that the king built the wall of Khorsabad 16,283 cubits long to correspond with the numerical value of his name. Gematria or isopsephy was borrowed into the Greek probably soon after their adoption of the Semitic writing system.
Maybe at first it doesn't seem like a big issue that we use this, possibly Hellenistic, method in Torah study. Until you find out there are multiple Halachot learned from gematria. Is there an opposing opinion about the origins of gematria? If not, how can we trust this method?