'broad-septate' originates from modern English compound formation combining 'broad' (Old English origin) and 'septate' (from Neo-Latin), where 'broad' meant 'wide' and 'septate' meant 'having a septum or partition'.

'septate' comes into English from Neo-Latin 'septatus' (past participle of Latin 'separare' / related to 'septum') used in scientific Latin to mean 'partitioned'; combined with the long-established English adjective 'broad' (Old English 'brād'), the compound 'broad-septate' formed in modern scientific usage to describe structures with wide septa.

Individually, 'broad' originally meant 'wide' and 'septate' originally meant 'having septa/partitions'; together the compound has retained those component meanings and now specifically denotes 'having wide internal partitions' in biological contexts.