I have taken the most interesting description of what Quillons are as a direct Quote viz; Quote''Collins dictionary quillon in British
( French kijɔ̃)
either half of the extended crosspiece of a sword or dagger
Collins English Dictionary. Copyright © HarperCollins Publishers
Word origin of 'quillon'
C19: from French, diminutive of quille bowling pin, ultimately from Old High German kegil club, stake.'' Unquote.
Of course to sword enthusiasts they appear to mean the crossguard in all the definitions I have seen and place the use first with Burton in Book of the Sword..which is remarkably late. Another definition points to the shape of a ninepin ...as in ninepin bowling...and it is true that the usual cross guard form follows this shape. For us however, in exploring Quillons we tend to think in terms of those curved extensions forward of the crossguard used to ensnare an opponents sword and protect the sword hand from a sliding blade cutting your hand. Having said that ...there are some interesting side shoots worth thinking about. Here's the bigger definition necessarily in full from http://www.worldwidewords.org/weirdwords/ww-qui3.htm; Quillon
Early in the history of sword-fighting it was realised that a guard between the blade and the hilt was essential to stop the blade of your opponent from sliding down yours and cutting into your hand. The quillons are the cross-pieces at right angles to the blade and hilt that serve this purpose.
Though swords have had them for many centuries, this word for them isn’t recorded in English until R F Burton’s The Book of the Sword in 1884
: “The quillons may be either straight — that is disposed at right angles — or curved.” (Before then, they seem simply to have been called cross-guards or just guards, as they often still are.) The origin is said to be the French quille, a ninepin, though that makes more sense when you learn the French also used it as a colloquial term for a leg, and so figuratively for the two legs represented by the jutting quillons. You may prefer to write the word as quillion instead, though this is less common.
In modern times, such technical terms have become useful in giving a sense of place and time in sword-and-sorcery fantasy tales, as here in a 1970 story by Fritz Leiber that was republished in 1995 in Ill Met in Lankhmar:
“He took a few shuffling steps, tapping the cobbles ahead with wrapped sword, gripping it by the quillons, or cross guard, so that the grip and pommel were up his sleeve — and groping ahead with his other hand.” The other spelling appeared in Oathbreakers by Mercedes Lackey (1989):
“The sheath looked as if it had once had metal fittings; there were gaping sockets in the pommel and at the ends of the quillions of the sword that had undoubtedly once held gemstones.”
The Oxford English Dictionary
used to suggest it be said as a French word, /kijɔ̃/ Help with IPA, roughly “kee-yon”, but with the final vowel nasalised as in French bon. However, the current edition confirms that most people Anglicise it to /ˈkwɪlən/ (“quill-on”).'' Unquote.