'echo-less' originates from Modern English, specifically the compound of 'echo' and the suffix '-less' (where '-less' ultimately comes from Old English 'lēas'), where 'echo' ultimately derives from Greek 'ēchō' meaning 'sound' and '-less' meant 'without'.

'echo' passed into English via Latin and Old French (from Greek 'ēchō'), and the productive English suffix '-less' (from Old English 'lēas') combined in Modern English to form compounds such as 'echo-less' (literally 'without echo').

Originally 'echo' meant 'a sound or repetition of sound' and '-less' meant 'without'; together they have retained the straightforward combined meaning 'without echoes' in modern usage.