Dactylology

Wow! a new word, a Webster 1913 nodeshell. m-w.com dates this at circa 1656 as a synonym for finger spelling, which it dates in the early 19th century. From Dactyl, a finger or toe; a digit. I assume it's relatively obsolete?

Dac`tyl*ol"o*gy (?), n. [Gr. da`ktylos finger + -logy.]

The art of communicating ideas by certain movements and positions of the fingers; -- a method of conversing practiced by the deaf and dumb.

⇒ There are two different manual alphabets, the one- hand alphabet (which was perfected by Abbé de l'Epée, who died in 1789), and the two-hand alphabet. The latter was probably based on the manual alphabet published by George Dalgarus of Aberdeen, in 1680. See Illustration in Appendix.

© Webster 1913