insociability 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.

1550s, "enjoying the company of others, disposed to be friendly and agreeable;" 1570s, "inclined to seek the company of others," from French sociable (16c.) and directly from Latin sociabilis "close, intimate, easily united," from sociare "to join, unite," from socius "companion, ally," from PIE *sokw-yo-, suffixed form of root *sekw- (1) "to follow." Related: Sociably.

As a noun, the name of a type of open four-wheel carriage with two seats facing each other (1780), an informal gathering for social purposes (1826, American English), and a couch with a curved, S-shaped back (1851).