'narrow-septal' is a compound of 'narrow' and 'septal'. 'narrow' originates from Old English, specifically the word 'nearwe', where 'nearwe' meant 'constricted' or 'tight'. 'septal' originates from New Latin/Latin, specifically the word 'septum', where 'septum' meant 'a fence' or 'partition'.

'narrow' changed from the Old English word 'nearwe' and eventually became the modern English word 'narrow'. 'septum' (Latin) passed into New Latin and formed the adjective 'septal', which was adopted into English to describe things relating to a septum.

Initially, 'narrow' meant 'constricted, tight' and 'septum' meant 'a fence or partition'; over time the compound came to be used specifically to describe an anatomical or structural partition that is unusually narrow ('having a narrow septum').