Dactylonomy n. : The art of numbering or counting by the fingers.

Example:


Taxonomy
World Wide Words, finger, weird words, e-magazine, finger game, hands, three bones, Etymology, English language, Ancillary, art, skill, embarrassment, After all, knuckle, joints, thumb, the Middle East.

Defination from the web:
... DACTYLONOMY/dæktɪlˈɒnəmɪ/ The art of counting on the fingers. To describe it so is to severely underestimate the skill of those who employed this technique. For it was not just a matter of using the whole finger, as some of us still ...