'equal-carpelled' is a compound formed from 'equal' + 'carpel' with the adjectival suffix '-ed'. 'equal' originates from Latin 'aequalis' (via Old French/Middle English) meaning 'level, even', and 'carpel' derives from New Latin 'carpella' ultimately from Greek 'karpós' meaning 'fruit'.

'equal' developed from Latin 'aequalis' into Middle English 'equal'; 'carpós' in Greek gave rise to New Latin 'carpella' and then modern English 'carpel'. The hyphenated compound 'equal-carpelled' arose in modern botanical English to describe pistils with similarly developed carpels.

Originally the elements referred separately to 'equal' and to 'carpel'; in botanical usage the compound came to mean specifically 'having carpels of approximately equal size or development'.