'equal-lobed' is a compound formed from 'equal' and 'lobe'. 'equal' originates from Latin 'aequalis' meaning 'level, even, equal', and 'lobe' originates from Greek 'lobos' through Latin 'lobus', meaning 'a rounded projection or division (a lobe)'.

'equal' passed into English via Old French and Middle English from Latin 'aequalis', becoming modern English 'equal'. 'lobe' came from Greek 'lobos' to Latin 'lobus' and entered English as 'lobe' in later medieval/early modern usage. The compound 'equal-lobed' arose in Modern English, especially in botanical and anatomical descriptions, to describe structures whose lobes are of equal size.

Separately, 'equal' originally meant 'level' or 'even' and 'lobe' meant a rounded projection; together in Modern English they specifically denote 'having lobes equal in size', a technical descriptive meaning in biology/botany.