[kronckew]

the pas d'ane is usually loops on both sides, the single one is as mentioned usually found on single edged blades. other weapons can have them too like my espada (pic below)

many sabres have this feature as a leather loop, sometimes missing in older swords, polish sabres may be found with thumb loops rather than forefinger ones. it aids control and improves the grip.

the pas d'ane on some smallswords is more decorative and not large enough to insert a finger. small swords with triangular blades do not really need indexing. the example i posted appears to be double edged, tho of course it's mostly a thrusting weapon that can cut a bit if sharp. with the full bow guard, the upper edge, while useful for back cuts, is not the main edge.

when i was fencing, i liked an italian grip, you could put two fingers thru the pas d'ane and strap the pommel to your wrist, aided and locked & strengthened the grip and as it was not a cutting weapon, did not need or benefit from having the wrist flexible.