1937, apparently coined by U.S. linguistics professor William Freeman Twaddell (1906-1982), from graph "letter, symbol" (see -graphy) + -eme "unit of language structure." Related: Graphemic.

"writing made by another person," by 1900, from allo- "other" + -graph "something written." Especially in law, "a deed not written by any of the parties to it." The linguistics sense of "form of an alphabetic letter" is from 1951; here the second element is abstracted from grapheme. Related: Allographic.