'irregular-flowered' originates from modern English as a compound of 'irregular' and 'flowered', where 'irregular' meant 'not regular' and 'flowered' meant 'having flowers'.

'irregular' comes from Latin 'irregularis' (via Old French and Middle English), and 'flowered' derives from Old English/Old French roots ('flor', Latin 'flos, floris') that became Middle English 'flower'; these elements combined in modern English to form the compound 'irregular-flowered' used in botanical description.

Individually, the components meant 'not regular' and 'having flowers'; over time their compound came to be used specifically in botany to denote flowers that lack radial symmetry (i.e., are zygomorphic or asymmetric).