How Well Do You Know English Slang?
late 15c., from French inhumanité (14c.) or directly from Latin inhumanitatem (nominative inhumanitas) "inhuman conduct, savageness," noun of quality from inhumanus (see inhuman).
And Man, whose heav'n-erected face
The smiles of love adorn,--
Man's inhumanity to man
Makes countless thousands mourn!
[Robert Burns, "Man was Made to Mourn," 1784]