According to Webster's Third New International Dictionary, Gothic has bandwa, "sign", from which Germanic *bandwa-, "sign", is reconstructed. From this comes Late Latin banderia, which Webster's hypothesizes has a Latin formative suffix, -arium. It could as well be from a Germanic plural. Banner comes from it, but the earlier meaning was not the cloth but the signs. Blazon has a similar origin from a different but synonymous root, *bhel-, at least in the sense of "sign." In Middle English it has the connotation of shield, but this also is a secondary development. Heraldry originates with the Roman army, who put their unit signs on shields but not flags. Banderia therefore imitate the shield blazons in cloth. Royal and national "blazons" go beyond the original intent, which was only unit identification, and are therefore a later development.
The original Germanic *gundfanon- meant "battle-flag". According to Webster's Third New International Dictionary, this descends through Old High German gunfano, "war flag" to Middle French and modern English gonfanon, a very rare word, and through Italian gonfalone to English gonfalon, synonymous with gonfanon. The modern terms have ceased to mean battle flags except when historians use them to refer to battle flags.