'cyanobacterial' originates from Modern scientific New Latin/English, specifically from 'cyanobacteria' with the adjectival suffix '-al', where the prefix 'cyano-' comes from Greek 'kyanos' meaning 'blue' and 'bacterium' comes from New Latin/Greek 'bakterion' meaning 'small staff' or 'rod'.

'cyanobacteria' was coined in modern scientific nomenclature in the 19th–20th century from Greek elements 'kyanos' and New Latin 'bacterium' and then formed the English adjectival derivative 'cyanobacterial' by adding the suffix '-al'.

Initially organisms now called 'cyanobacteria' were described as 'blue-green algae' (algal), but over time they have been reclassified as photosynthetic bacteria; the adjective shifted from an algal sense to a bacterial/phylogenetic sense.