'smooth-spoken' originates from the combination of 'smooth' and 'spoken', where 'smooth' meant 'having an even and regular surface' and 'spoken' is the past participle of 'speak'.

'smooth-spoken' evolved from the Old English word 'smōð' meaning 'smooth' and 'specan' meaning 'to speak', eventually forming the modern English word 'smooth-spoken'.

Initially, it meant 'speaking in a smooth manner', and this meaning has largely remained the same in modern usage.