means The state or habit of being late, of arriving after the agreed or expected time.

from From the Latin 'tardus,' meaning slow or sluggish, which strolled into Old French as 'tardif' and ambled on into Middle English as 'tardy.' The abstract noun 'tardiness' was built by stacking the English '-ness' onto 'tardy,' turning a slow adjective into a slow condition. The same Latin root unhurriedly fathered 'retard' and 'tardigrade,' that famously plodding 'slow-stepper' water bear.