'soundly-built' originates from the combination of 'soundly,' meaning 'in a thorough and reliable manner,' and 'built,' the past participle of 'build,' meaning 'to construct.'

The term 'soundly-built' evolved from the Old English word 'byldan,' which meant 'to build,' and 'sound,' from the Old English 'gesund,' meaning 'healthy' or 'safe.'

Initially, 'soundly-built' referred to structures that were 'safely constructed,' and this meaning has largely remained the same in modern usage.