hard-hearted

The compound adjective 'hardhearted' is a transparent formation from native English elements. The first element, 'hard', carries its ancient Germanic sense of being firm, resistant, or severe, which extends metaphorically to character. The core element, 'heart', has long been the linguistic seat of emotion, compassion, and inner life in English, stemming from Proto-Germanic. The suffix '-ed' simply denotes possession of these qualities. Thus, the literal construction "having a hard heart" directly and logically yields the modern meaning of being emotionally callous, unfeeling, or pitiless, as if one's emotional core were physically hardened and impervious to the suffering of others.