'bacterioscopical' originates from a modern formation combining Greek 'bakterion' (meaning 'small staff, rod') and Greek 'skopein' (meaning 'to look'), via New Latin/Neo-Latin elements such as 'bacterioscopy', plus the English adjectival suffix '-ical'.

'bacterioscopical' changed from the noun 'bacterioscopy' (a 19th-century New Latin/English formation) by adding the English suffix '-ical' to form the adjective 'bacterioscopical'.

Initially, it meant 'relating to the microscopic observation of bacteria', and over time its meaning has remained essentially the same in technical contexts.