As the shield was beginning to fall out of use, plate armor was becoming common, and there were more instances of sword-on-sword combat, most swords seen on the battlefield were a variety of Bastard-swords. To attain better control over the blade, many swordsmen looped their first index finger over the guard. This was becoming so common that small ring-like extensions of the hilt, called annelets, were being crafted onto the hilt which would protect the finger in the off-chance that a blade would slide down to the ricasso and give someone a nifty battle scar.
This new trend found its way onto many swords, with the first examples being solitary annelets on one side of the ricasso, which could first be seen indiscriminantly throughout Europe ca.1320 C.E.
More hilt modifications followed, presenting more intricate and useful methods of digital protection and point manipulation:
ca.1420-Dual annelets, also called anneus or ports appearing commonly.
ca.1460-Combinations of annelets and another type of hand protection, called side-rings, show up. Side rings were somewhat larger than annelets and were placed on the long sides of the guard, running parallel to it. These were the first additions to medieval swords that were put in place to guard the hand itself.
ca.1470- The first knuckle-guards seen on hilts, the precursor to the incredibly ornate hilts of the Musketeer era.
Such additions were grandfathers of the elaborate swept-hilt rapiers of the middle and late Rennaissance and tailored to the new kind of solder who had casted off his steel gauntlets in place of leather gloves.
Medieval Swordsmanship, by John Clements
European Weapons and Armor, by R.E. Oakeshott