Turns out that this kind of safety glass is, terminologically, really toughened glass, which I know as tempered glass. Sounds like the toughening process resembles the quenching/tempering of metal.
Following a WikiPee rabbit hole I discovered lead me to Prince Rupert’s Drops. Strange thing: drip droplets of molten glass into cold water; recover when cool. They will have an elongated teardrop shape. Try to crush the bulb; it will be hugely resistant. Snap, break, or crush the skinny tail, and the whole thing will fragment into dust. So I have read. Apparently the tail and the outside of the drop cool faster than the inside, which stays molten a bit longer, yielding a tensile stress pattern that makes the tail weak and the bulb strong. Or something like that.
Anyway, I think this is auto window-glass, fragmented into cuboidal shards.
My other research adventure today had to do with the royal sites of Ireland…medieval period…there are four of them. Five. Six. Depends on the definition.
Wait. One more research adventure: KW taught me what a zarf is. I told JCB, and he said nooooooo…then looked it up. From a Turkish term, he says.
I am now more learn ed, that is learned pronounced with two syllables.