'calcium-poor' is a modern English compound formed from 'calcium' and 'poor'. 'Calcium' originates from New Latin 'calcium', ultimately from Latin 'calx' meaning 'lime'. 'Poor' originates from Old French 'povre', from Latin 'pauper' meaning 'poor, needy'.

'calcium' developed from Latin 'calx' to New Latin 'calcium' and then into the modern English scientific term 'calcium'. 'Poor' evolved from Latin 'pauper' to Old French 'povre' and Middle English forms such as 'povre/poore', becoming modern English 'poor'.

Initially, 'calx' and related forms referred to lime or limestone; over time 'calcium' became the name of the chemical element. 'Poor' originally denoted a person lacking wealth ('pauper') and broadened to describe lack or insufficiency generally (e.g., 'lacking in X').