'newly-hired' originates from English, specifically the adverb 'newly' (from 'new') combined with the past participle 'hired' (from 'hire').

'new' comes from Old English 'nīwe' (related to German 'neu'), and 'hire' comes from Old English 'hȳran' meaning 'to employ, give someone work'. The compound phrase formed in modern English by combining the adverb + past participle to describe someone 'having been hired recently'.

Individually, 'new' originally meant 'recent' or 'not long ago', and 'hire' meant 'to give work or reward for service'; together the phrase has come to mean 'recently employed' with little change in core meaning over time.