As it turns out, a glaive is one of the most often forgotten pieces of the medieval collections maintained by serious medieval weapons enthusiasts around the country. Not only is the glaive easily confused with other things, because of its cult film legacy, but it’s also a big weapon, and somewhat specialised, therefore, hard to come by. The glaive is also very old, and has passed out of popularity in favor of swords in all their forms. Many people who collect medieval weapons will have a variety of swords, and blades in a variety of cultural forms, if not genuinely from around the world. Very few have bothered to seek out any glaives.
In fact, glaive is French; it is the modern word for sword, and is poetically used in the stead of the more accepted and cliche ‘sword’ –I suppose it’s more romantic? Modern etymogology trace the roots closest to the early terms for swords, but, even in medieval times, the glaive was always used to refer to polearms, and spears. A glaive is what a spear wants to be when it grows up; while the spear is great for throwing, a glaive is meant to be wielded and held. It looks like a very fancy spear; long handle, with a blade affixed to the end.
The glaive’s blade is often wrought in designs. Typically, they were used to take riders right off a horse, without being close enough to get trampled or caught by a sword. So they were long, and they were designed to get a grip on whatever they went into. A man suffering from a piercing wound can still swing a sword, so the glaive’s design was fairly innovative. It was thin enough to get into tight crannies between plates of armor, and it was hooked, pronged, or had serrated star-shaped notches cut into it, protruding from it, etc., and wrought with ornate lacework. Ideally, the glaive would be thrust between plates of armor, securely locked into bone and gristle, and tear the rider down, making him easier to kill.
An armed cavalry is death to any foot soldiers and infantry, so the evolution of the polearm probably began at spears, and went from there. The riding men were a double threat; they could trample you, or cut men down with swords. The people on the ground had to have something to kill the rider, and take the horse as much out of commission as possible, keeping the rider and horse as far away as possible in the meantime.