'widely-employed' originates from English, specifically combining the adverb 'widely' (from Old English 'wīd' meaning 'broad' plus the adverbial suffix '-ly') and the past participle 'employed' (from the verb 'employ', from Old French 'employer').

'employ' changed from Old French 'employer' into Middle English forms such as 'employen' and eventually became the modern English verb 'employ'; 'widely' developed from Old English 'wīd' with the suffix '-ly' to make an adverb, and the compound/phrase 'widely employed' has been used in modern English to mean 'extensively used'.

Initially, 'employ' carried the sense 'to use or apply' (from Old French usage), and over time it retained this core sense while also developing the specific sense 'to hire'; in the compound sense 'widely employed' the meaning has remained 'used extensively'.