The quality or state of being heated emotionally; intense anger or passion.
From 'heated' + '-ness' (Old English '-nis,' a suffix forming abstract nouns). The '-ness' suffix has been productively used in English since Old English times to create abstract qualities.
English speakers love stacking suffixes—we can say 'heat,' 'heated,' 'heatedly,' and 'heatedness,' each adding layers of abstraction. By the time you get to 'heatedness,' you've moved from a physical phenomenon all the way to describing a personality trait.
Complete word intelligence in one call. Free tier — 50 lookups/day.