the capacity for sustained mental and physical effort
Latin stamina, pl of stamen warp thread. Originally in the sense ‘the essentials or rudiments’ of something, likened to the warp threads of cloth; the current sense comes from the use of Latin stamen to refer to the thread of a person's life spun by the Fates, hence the life force each person possesses at birth, the strength of which, barring accidents, determines the length of their life