'annularia' originates from Latin, specifically from 'annularis' (related to 'annulus'), where 'annulus' meant 'ring'.

'annularia' passed into Neo-Latin/botanical Latin as a technical name for ring-arranged (whorled) foliage and was adopted in paleobotanical usage as the form-genus name 'annularia'.

Initially it meant 'pertaining to rings', but over time it evolved into the specialized scientific meaning 'a form-genus name for whorled fossil leaves (Calamites)'.