gravamen
Concise Oxford English Dictionary © 2008 Oxford University Press:
gravamen /grəˈveɪmɛn/
▶noun (pl. gravamina /-mɪnə/) chiefly Law the essence or most serious part of a complaint or accusation.
– origin C17: from late L., lit. ‘physical inconvenience’.
'gravamen' also found in these Oxford entries:

