habitumbra
noun
The experience of performing a simple, repetitive task so often that it becomes subconscious, leaving the mind free from active thought. While doing this, one becomes detached from surroundings, with no awareness of noise or silence.
From Latin 'habitus' (condition, habit) + 'umbra' (shadow), indicating the shadow of habitual action that obscures awareness. Pronounced "hah-bih-TOOM-brah"