'epidote-poor' is a modern compound formed from 'epidote' + 'poor'. 'epidote' ultimately comes from Greek 'epidotos' (via Modern Latin 'epidotus' and French 'épidote'), where the Greek element meant 'given in addition'; 'poor' comes from Old French 'povre' and Latin 'pauper', meaning 'having little'.

'epidote' changed from Greek 'epidotos' → Modern Latin 'epidotus' → French 'épidote' and entered English as 'epidote'. 'poor' evolved from Latin 'pauper' → Old French 'povre' → Middle English 'poor', retaining a sense of lacking or having little.

Initially 'epidote' carried the Greek sense of 'given in addition' and later became the proper name of a specific mineral; 'poor' originally referred to having little wealth and broadened to mean 'lacking' in any substance. The compound now specifically denotes 'lacking epidote'.