The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A suffix which is a null morpheme, used in models of linguistic analysis to represent the lack of a suffix where one might otherwise be expected (for example, as one of several inflections that a stem can take, or the reduction of a historically vocalised suffix to the point that it is inaudible). Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.