baek for meI shen
noun
definition: in linguistics, a word that appears to be the base of, but was actually formed from, another word, as “trivia” from “trivial.”
Other examples of back formations
injure (from injury), liaise (from liaison), enthuse (from enthusiasm), euthanase or euthanize (from euthanasia), edit from editor
Explanation
As a kind of word formation in English, back formation is a bit like derivation in reverse. The process of derivation adds a prefix or suffix to an existing word to form a new word. “National” is a derivation of “nation” (nation + -al), “nationalism” is a derivation of “national” (national + -ism), and “international” is a derivation of … “national” (inter- + national). Back formation removes an affix, commonly a suffix, from an existing word (“-ia” from “euthanasia”) to form a word wrongly assumed to be the base of the first word: “euthanase” or “euthanize.”