rigor1

 
Pronunciation: /ˈrɪgɔː, ˈrʌɪgɔː, -gə/

noun

Medicine
  • a sudden feeling of cold with shivering accompanied by a rise in temperature, often with copious sweating, especially at the onset or height of a fever.
  • short for rigor mortis.

Origin:

late Middle English: from Latin, literally 'stiffness', from rigere 'be stiff'