word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."
In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.
"to mark or blot out as with a pen, erase (words), obliterate," c. 1600, from Latin expungere "prick out, blot out, mark (a name on a list) for deletion" by pricking dots above or below it, literally "prick out," from ex "out" (see ex-) + pungere "to prick, pierce" (from suffixed form of PIE root *peuk- "to prick").
According to OED, taken by early lexicographers in English to "denote actual obliteration by pricking;" it adds that the sense probably was influenced by sponge (v.). Related: Expunged; expunging; expungible. In U.S. history, the Expunging Resolution was adopted by the Senate in 1837 to expunge from its journal a resolution passed by it in 1834 censuring President Jackson.
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Definitions of inexpungible
not capable of being expunged; "the inexpungible scent of a bottle of perfume he had broken"- Louis Auchincloss;