Back Form

If affixation means forming a word by adding an affix (e.g. frosty from frost, refusal from refuse, instrumentation from instrument), then back-formation is essentially this process in reverse: it adapts an existing word by removing its affix, usually a suffix (e.g. sulk from sulky, proliferate from proliferation, back-form from back-formation). ❋ Unknown (2009)

But the adjective ginger has been obsolete for a long time, and it's notable that nobody is tempted to back-form it anew, as in "his ginger handling of the question," which is what you'd expect if the adverbial gingerly were really analyzed as composed of the root ginger plus the derivational suffix -ly. ❋ Unknown (2004)

When my evening-school had been in operation a few weeks, I noticed, one evening, at the end of the back-form on the girls 'side a new face. ❋ Various (N/A)

On several occasions, when some unusually intelligent little creature would come from a back-form, and solve a question which had bewildered those in front, there was a sensible expression of delight over the whole school. ❋ Various (1836)

Interestingly, if you back-form ‘disappointed’, you change its meaning substantially enough to make it entirely inappropriate: “Winter’s piece appointed me …” ❋ Unknown (2009)