'heartlessness' originates from the Old English word 'heorte,' meaning 'heart,' combined with the suffix '-less,' indicating 'without,' and '-ness,' forming a noun indicating a state or quality.

'heorte' transformed into the Middle English word 'hert,' and eventually became the modern English word 'heart.' The suffix '-less' has been used since Old English to denote 'without,' and '-ness' has been used to form nouns from adjectives.

Initially, it meant 'without heart or compassion,' and this meaning has largely remained the same in modern usage.