the word strenuous entered english in the late 16th century, directly from latin strenuus, which meant active, vigorous, or brisk. the latin term itself is of uncertain origin, though it may be related to ancient greek strēnḗs, meaning strong or hard. the core semantic thread from its classical roots to modern english is the concept of forceful, energetic activity. over time, the meaning evolved to emphasize not just vigor itself, but the demanding nature of tasks requiring such vigor, leading to its current primary sense of requiring great effort.

Structure: strenu (active, vigorous) + ous (adjective suffix) strenu (from latin strenuus, meaning active, vigorous, brisk); ous (from latin -osus, a suffix forming adjectives meaning "full of, prone to")