'widely-watched' is a compound formed from the adverb 'widely' and the past participle 'watched' (the past form of 'watch'), where 'widely' means 'to a wide extent' and 'watched' indicates that something is observed.

'widely' derives from Old English 'wide' + suffix '-ly' (forming an adverb); 'watch' originates from Old English 'wæccan' (to be awake, to watch) via Proto-Germanic roots, and its past participle 'watched' developed as the regular past form in Modern English. The compound arose by combining the adverb and past participle to describe extent + observation.

Individually, 'wide' originally meant 'broad' and 'watch' originally emphasized staying awake or guarding; over time 'widely' came to mean 'to a broad extent' and 'watch' to mean 'observe', and together the compound evolved to mean 'observed by many people' or 'attracting broad viewership'.