Back-formation is one of several methods by which new words are added to the language. An often-quoted example is the word pea. Before pea was created by back-formation, English had the singular noun pease. Here are two examples of its early use from the OED, (some spellings altered):
All this world’s pride is not worth a pease.
As like as one pease is to another.
The plural was peasen:
The leaves of beans and peasen
Cherries, gooseberries, and green peasen
Over time, as -s shoved out -en as the sign of the plural, speakers came to feel that pease was a plural; thus was born our singular pea and its plural form peas.
Back-formation is especially frequent in the creation of new verbs. Some writers use the verb “to back form,” a back-formation of back-formation; so far, this coinage hasn’t made it into either the OED or M-W.
Sometimes the coinage is intentionally jocular, as with the verb buttle from butler: “Nobody could buttle like James…” Sometimes the new verb formed from a noun fills a need and is quietly absorbed into the language, like the verb edit from editor.
At their first appearance in the language, back-formations often stir feelings of revulsion. Test your own reactions to the following sentences:
I hate it when people enthuse too much over food.
I’ve met him twice, but never had the chance to conversate.
To what extent…did the US intelligence community surveil the anti-apartheid movement in the United States?”
Now I would never dis my own mama just to get recognition.
Britain’s most senior police officer is liaising with US law agencies….
Have you accepted the legitimacy of the back-formations that have created the verbs enthuse, conversate, surveil, dis (also spelled diss), and liaise? Or do you get that fingernail on the blackboard feeling when you see them or hear them?
Conversely, gauge your reaction to these verbs: diagnose, donate, eavesdrop, evaluate, kidnap, manipulate, proliferate, and vaccinate.
My guess is that the second list raised nobody’s blood pressure. Yet, each of the verbs in this list is a back-formation from a pre-existing noun: diagnosis, donation, eavesdropper, evaluation, kidnapper, manipulation, proliferation, and vaccination.
Time and usage will determine whether back-formations like surveil and conversate will prevail. The determining factor will be usefulness. If the coinage is felt to fill a gap in the language, speakers will eventually embrace it.