the.com/incompetency

means A lack of the skill, ability, or legal capacity needed to do something properly.

from Built from the Latin prefix 'in-' (not) plus 'competentia' (fitness, capacity), itself from 'competere' — literally 'to strive together' or 'to be fit for' — the same root that gives us 'competent' and 'compete.' English borrowed the positive form first, then simply negated it to name its absence; the word has long done double duty, judging both a person's skill and, in law, their very capacity to act.