'Calamites' originates from New Latin (botanical), specifically the Latinized Greek word 'Calamites', where 'kalamos' meant 'reed' or 'hollow stalk'.

'Calamites' derives from Greek 'kálamos' → Latin 'calamus' (meaning 'reed'), later adapted in Neo-Latin botanical nomenclature as the genus name 'Calamites' and adopted into English usage for the fossil plants.

Initially it referred broadly to reed- or reed-like plants; over time it came to denote this specific fossil genus of tree-like horsetails.