The "end of day" description comes from the idea that a glassworker, at the end of his/her workday making beads or other glass items, has a collection of crumbs and broken tail ends of glass rods that they "cleaned up" by making a few beads and rolling them in the crumbs.

The story is probably apocryphal since the most of crumb beads I've handled do not seem to be "one-offs" - they appear to be deliberately decorated with a uniform selection of colors, sizes, etc. The exception may be some of the large & chunky Venetian trade beads with highly irregular decoration.

I'll look for an example of the large beads I'm thinking of and post it in a bit.