'bannerless' is formed from the noun 'banner' + the adjective-forming suffix '-less' meaning 'without'. 'Banner' originates from Old French 'baniere' meaning 'flag, standard', and the suffix '-less' comes from Old English '-lēas' meaning 'free from' or 'without'.

'banner' entered Middle English from Old French 'baniere' (also recorded as 'banere' or 'banier'), itself from a Late Latin/Frankish root referring to a sign or flag; the adjective suffix '-less' comes from Old English and was attached to nouns to form adjectives (e.g. 'homeless'). Together they produced the modern compound adjective 'bannerless'.

Initially, 'banner' meant a physical flag or standard used as an ensign; 'bannerless' originally meant 'without a physical flag or standard.' Over time the term has also come to be used figuratively (e.g., lacking a header, title, or conspicuous identifying banner).