The real source of stamina

When you talk about someone's stamina you are literally saying that he or she is at the mercy of the Fates.  

Stamina is the plural of the Latin word stamen (thread), which of course has given us the word for the threadlike part of a flower.

But stamen was also used to mean the thread spun by the three Fates in Greek and Roman mythology, the length of which determined one's life. 

Her stamina has definitely run out

When "stamina" first came into English around 1700, it was as the plural of this word "stamen". Maintaining the metaphor of the thread spun by the Fates, it meant all the bodily characteristics that could be expected to determine one's life expectancy. That sense died out, leaving us with the current meaning, the capacity to endure fatigue and exertion. 

The word ceased to be plural and became a singular. Knowing this may come in handy the next time someone berates you for using "media" or "data" with a singular verb. Would they say "Her stamina are extraordinary"?