incommodity (n.)

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.

1786, "decorative chest of drawers for holding clothes, handy articles, etc.," earlier (1680s) name of a type of fashionable ladies' large, high headdress mounted on a wire frame, from French commode, noun use of adjective meaning "convenient, suitable," from Latin commodus "proper, fit, appropriate, convenient, satisfactory," from com-, here perhaps an intensive prefix (see com-), + modus "measure, manner" (from PIE root *med- "take appropriate measures"). Meaning "chair housing a chamber pot," usually kept in a bedroom, is first attested 1851 from notion of "convenience."

I wash'd and patch'd, to make me look provoking,

   Snares that they told me wou'd catch the men;

And on my head a huge commode sat cocking,

   Which made me shew as Tall agen:

[from a song in "Wit and Mirth," 1719]