Vexillology: The study of flags. Coined by Whitney Smith in 1957, as a combination of the Latin word Vexillum and the Greek suffix -ology.
Vexillum (pl. vexilla): In ancient Rome, a square military banner hung from a crossbeam carried on a staff. It’s the diminutive of velum (“sail”), itself derived from Proto-Indo-European *weg- (“to weave a web”) or *weǵʰ- (“to ride”), thus “that which propels”.
Vexilloid: Another term coined by Whitney Smith, which he defined as “an object which functions as a flag but differs from it in some respect, usually appearance. Vexilloids are characteristic of traditional societies and often consist of a staff with an emblem, such as a carved animal, at the top.” Smith derived the word from one of its primary examples, the vexillum.
Here’s the oldest (and only) surviving vexillum:
The only extant Roman vexillum, 3rd century AD. Pushkin Museum of Fine Arts, Russia. Licensed under Public Domain via Wikimedia Commons.