arithmancy

[ ar-ith-man-see ]
/ ˈær ɪθˌmæn si /

noun

divination by the use of numbers, especially by the number of letters in names.
Also a·rith·mo·man·cy [uh-rith-muh-man-see, ar-ith-] /əˈrɪθ məˌmæn si, ˈær ɪθ-/.

Origin of arithmancy

1570–80; < New Latin arithmomantia < Greek arithmó(s) number + manteía -mancy