I learned "anneal" in the bad old days before Pyrex glass
became available. For instance, if one tube had to be joined
to the end of another, the flame had to be very hot to make
glass of each end fuse,obliterating the seam. But then you
had to cut off the oxygen, lowering heat of flame very much,
and let the molten place slowly drop below melting point,
or the joint would be very fragile.
The opposite was "Prince Rupert drops" made by melting a rot of glass over a dish of water, and letting the molten drops with a moderate tail fall into the water. When removed
breaking even a tiny bit off the tail caused the who glass
to shatter.
Automobile windshield used to be annealed. But then when they broke, sword shaped pieces with horribly sharp edges
hit passengers in the face. So now windshields are tempered
so that even a small scratch may cause them to shatter into
hundreds of fingernail sized pieces.