I'm running a fever/temperature.
I have a student who likes to ask where idioms come from. Since the meanings are not literal, it is challenging for her to remember them. It often helps her to attach a story or explanation to an idiom, even if it is only folk etymology.
I've not had any luck searching on EL&U or in any dictionary for the origins of the phrase. It's always present in dictionaries but for etymology just refers the reader to run, which never explains the specific meaning in running a fever/temperature.
If anyone knows where the phrase actually originates, it would be helpful, but even a non-referenceable* etymology would be useful.
*i.e. heard from some guy down the pub; learnt a long time ago but I forget where; made-up; etc.
Best Answer
I'm not sure of the actual entymology of the phrase, but 'to run' means in this case 'to continue to have', so while the fever is being maintained it's 'running'.