c. 1200, cruelte, "indifference to, or pleasure taken in, the distress or suffering of any sentient being," from Old French crualté (12c., Modern French cruauté), from Latin crudelitatem (nominative crudelitas) "cruelty," from crudelis "rude, unfeeling; cruel, hard-hearted," related to crudus "rough, raw, bloody" (see crude). Meaning "a cruel act" is from late 14c.
"a grip, grasp, tight hold," c. 1200, plural, cleches, from or related to the verb clucchen, clicchen (see clutch (v.)). Clutches "the hands," suggesting grasping rapacity or cruelty, is from 1520s.
"barbarous cruelty," late 15c., from French inhumanité (14c.) or directly from Latin inhumanitatem (nominative inhumanitas) "inhuman conduct, savageness; incivility, rudeness," noun of quality from inhumanus "inhuman, savage, cruel" (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]
1530s, "enormous wickedness," from French atrocité or directly from Latin atrocitatem (nominative atrocitas) "cruelty, fierceness, harshness," noun of quality from atrox "fierce, cruel, frightful," from PIE *atro-ek-, from root *ater- "fire" + root *okw- "to see;" thus "of fiery or threatening appearance." The meaning "an atrocious deed" is from 1793.
Is Moder was ded, his fader nam an oþur wijf. ... seint Edward heo louede luyte, for stepmoder is selde guod. ["South English Legendary," c. 1300]