'lifelessly' originates from English, specifically formed from the adjective 'lifeless' + the adverbial suffix '-ly', where 'life' (from Old English 'līf') meant 'life' and the suffix '-less' (Old English 'lēas') meant 'without'.

'lifelessly' changed from Middle English formations based on 'life' + the suffix '-les(s)' (e.g. Middle English 'lifeles') and later the Modern English adjective 'lifeless', and the adverb was formed by adding '-ly' to make 'lifelessly'.

Initially, the components meant 'without life' (i.e. 'lifeless'); over time the adverbial form came to mean 'in a manner lacking vitality or animation' and has been used to describe actions or expressions that show no energy or feeling.