aplomb
Self-confidence; poise; composure.
uncountable
His nonchalance and aplomb during hard times have always been his best character trait.
The apparent elegance and precision exhibited by a confident, accomplished dancer.
uncountable
The perpendicular; perpendicularity.
uncountable
Where it comes from
Unadapted borrowing from French aplomb (“plumb line”).
Adapted from the Wiktionary entry aplomb (CC BY-SA 4.0).