Arithmancy

Definition: the historical name for numerology (before the 20th century) — "divination by numbers," from the Greek arithmos ("number") and manteia ("divination"). The word "arithmancy" dates to the 1570s, while "numerology" in English is attested only from approximately 1907. Agrippa in the 16th century applied arithmancy to the Latin alphabet in De occulta philosophia (A–I = 1–9, K–S = 10–90, T–Z = 100–900; U, J, W were not yet considered letters).

[source: Numerology — Wikipedia (en); Agrippa — esotericarchives] Related: numerology, izopsefiya, history of numerology.