Absent-minded means forgetful because your thoughts are elsewhere. An absent-minded professor, absent-minded about keys, absent-mindedly stirring.
It is affectionate and excuses the lapse, since somebody absent-minded is thinking hard about something else rather than not thinking at all. The absent-minded professor is a fixed comic character.
1adjectiveabsent-mindedForgetful because your thoughts are elsewhere.
“My absent-minded uncle once went to work in his slippers.”
absent-minded is a quality.
From the phrase absent mind plus -ed, meaning having a mind that is elsewhere.
From absent mind + ed, meaning having an absent mind.
Etymology from Wiktionary, CC BY-SA
Practised in Thinking & Memory