rigor

The word rigor entered English in the late 14th century via Old French, tracing back to the Latin rigor, meaning stiffness or numbness. This Latin term derives from the verb rigēre, to be stiff, which itself is linked to the Proto-Indo-European root reig-, meaning to stretch tightly or bind. The core semantic thread from physical stiffness evolved logically: first to metaphorical stiffness as severity or strictness in principles, then to the harshness of conditions, and finally to the physiological stiffness and shivering of a fever chill. Thus, the modern abstract meanings of strict precision and harshness retain a conceptual link to the ancient sense of inflexible tightness.

Structure: rig (stiff) + or (noun suffix) rig is from Latin rigor (stiffness, numbness, severity), from the verb rigēre (to be stiff). The suffix or is a Latin noun-forming suffix indicating a state or condition.