What word or phrase does your mother always say?
late 14c., "numeral below 10," from Latin digitus "finger or toe" (also with secondary meanings dealing in counting and numerals), related to dicere "tell, say, point out" (see diction). Numerical sense is because numerals under 10 were counted on fingers. The "finger or toe" sense in English is attested from 1640s.
digit dig·it (dĭj'ĭt)
A finger or toe; dactyl.
A telephone number: Did you get her digits