"Fress" is a word that passed into English from Yiddish "fresn" (to devour) and German "fressen" (to eat, but used to refer to animals' or excessively messy human eating; "essen" is the verb for normal human eating). The English usage is to devour or stuff oneself, to pig out. Americans often add the English suffix "-ing" to make "fressing."
One excerpt from a Ukrainian Jewish book, The Book of Horodenka, says the Yiddish word also means "winter frost," leading to jokes such as "I have an attendant who is completely winterized: His beard is as white as snow, and he fresses."
"FRESS" is also an acronym for "File Retrieval and Editing System" (presumably the extra S is added for pronunciation purposes or to look like the Yiddish-derived verb). It was an early hypertext document system which let authors create links within any text document or among any number of text documents. It was developed in 1968 at Brown University by Andries "Andy" van Dam to run on an IBM mainframe running VM/CMS.
FRESS was a milestone in several ways. Unlike its predecessor, Hypertext Editing System, it allowed some non-text symbols, characters, and graphics to be shown; it did not limit the size of the information being dealt with; its links were bi-directional, it was independent of particular I/O media; and it had the first ever "Undo" capability of a computer program. It was also the first hypertext system to be used in teaching (a
Brown University poetry class).