'regular-petaled' is a modern English compound formed from 'regular' and 'petaled'. 'Regular' originates from Latin 'regularis' (from 'regula' meaning 'rule, straight edge'), and 'petal' originates from Greek 'petalon' meaning 'leaf' or 'thin plate'.

'regular-petaled' developed in botanical English by directly combining the adjective 'regular' (from Latin via Middle French/English) with the past-participial adjective-form of 'petal' (from Greek 'petalon' via New Latin 'petalum'), becoming a descriptive compound used in floriculture and botanical descriptions.

The component words originally meant 'rule/straight' (regular) and 'leaf/plate' (petal); combined in modern usage they specifically describe the orderly, uniform arrangement of a flower's petals rather than the separate original senses.