'diathermancy' originates from Greek, specifically the word 'diathermasia,' where 'dia-' meant 'through' and 'thermasia' meant 'heat.'

'diathermasia' transformed into the French word 'diathermansie,' and eventually became the modern English word 'diathermancy' through scientific terminology.

Initially, it meant 'the ability to transmit heat,' and this meaning has largely remained the same in modern usage.