'regular-flowered' originates from English, specifically the words 'regular' and 'flowered', where 'regular' ultimately comes from Latin 'regularis' (from 'regula') meaning 'according to rule' and 'flowered' derives from Old English 'flor'/'flōwer' meaning 'bloom'.

'regular' came into English via Latin 'regularis' (from 'regula' 'rule') through Old French and Middle English to become the modern English 'regular'; 'flowered' is built on the noun 'flower' (Old English 'flor'/'flōwer'), forming the compound adjective 'regular-flowered' in botanical usage.

Originally 'regular' meant 'according to rule' and 'flowered' meant 'having flowers'; in botanical contexts the compound came to be used specifically for flowers that are symmetrical around a central axis (radially symmetrical).