naval gunfire in the Nelson era.

[Etranger]

...
I was always fascinated by the phenomenon of "wind of ball" where a cannonball passing close to someone's head or abdomen would leave them ostensibly unhurt, then they would collapse within hours of the battle and die a couple of days later (the Imperial Guard Horse Grenadier rendered mute for life after a "near miss" at Friedland is another example). Apparently, this was much more likely to be fatal at sea than on land, so I suspect it may have had something to do with the larger calibres of gun being used.

Possibly caused by the phenomenon sometimes called 'cavitation' where the changes in air pressure cause internal damage, without an external wound - as repeatedly reported in accounts of more modern wars. Now called Blast Injuries https://en.wikipedia.org/wiki/Blast_injury although obviously the cannon balls in Nelson's day were usually solid, not explosive.

[MarshalNey]

I had heard a similar story from the war of 1812. The British abandoned a fort and blew up the gunpowder supply. Many of the advancing Americans were killed by the blast with no apparent injuries.

[HMS Priapus]

Etranger is spot on. Blast injuries are the likely cause.

Look at the SDZ - Surface Danger Zone of a modern tank as an interesting point of comparison.

[BaronVonWreckedoften]

There seems to be a body of thought that "wind of ball" in the black powder era was more psychosomatic than shock-wave based, given the relatively low velocities of cannonballs compared to modern munitions. However, that doesn't explain the symptoms experienced by some victims, which correlate to serious brain/abdominal injuries. And yet.....it does seem to be difficult to reconcile people dying almost instantly from the shock wave of a large explosion, and others dying hours, or even days later after a near miss from a relatively small object going at subsonic speed.

[Jeremy]

I thought ‘wind off ball’ was when Peeler directed his farts forward.

[BaronVonWreckedoften]

Some say you can hear them clanking when he does that.

[Peeler]

Ooh there you go again, cheeky feckers

This death after a few days, would the passing ball cause a small rupture somewhere in the victim, and then get progressively worse until he popped off?

[Etranger]

Ooh there you go again, cheeky feckers

This death after a few days, would the passing ball cause a small rupture somewhere in the victim, and then get progressively worse until he popped off?

That seems to be some of what happens.