Isopsephy is the Greek word for the practice of adding up the number values of the letters in a word to form a single number.
Derived from the Greek isos ('equal') and psephos ('pebble')
The early Greeks used pebbles arranged in patterns to learn arithmetic and geometry.
Isopsephy first emerged as a literary phenomenon in Greek during the Hellenistic period, not much before earlier than the first century A.D. It was adopted from the Greeks in the first or second century A.D., and later used in Arabic.
Isopsephy is related to Gematria, the same practice using the Hebrew alphabet, and the ancient number systems of many other peoples (for the Arabic alphabet version, see Abjad numerals). A Gematria of Latin-script languages was also popular in Europe from the Middle Ages to the Renaissance and indeed its legacy remains in numerology and Masonic symbolism today.
It was built upon the ancient convention of assigning the letters of the alphabet numerical values. Letters, words, or entire sentences could then be composed or interpreted based upon the sum of their numerical values.