Incompetence is not being good enough at the job. Sheer incompetence, sacked for incompetence, gross incompetence.
The Peter principle is the famous joke about it: people rise until they reach a job they cannot do, and there they stay. In law, incompetence also means lacking the legal capacity to do something, which is a technical matter rather than an insult.
1nounincompetenceNot being good enough at the job.
“The manager was sacked for incompetence after losing the company's biggest client.”
incompetence is a failing.
French incompetence is in-, not, plus competence, from Latin competere, to be suitable or fit.
French
incompétence
English, today
incompetence
From French incompétence, equivalent to in- + competence.
Etymology from Wiktionary, CC BY-SA