Crumbs!

This coming Monday is Canada Day, traditionally a time for outdoor eating, much to the enjoyment of ants and sparrows who can scarf down the attendant crumbs.

"Crumb" has meant a small piece of bread since Anglo-Saxon times, but the interesting question is, why is it spelled with a silent b?

Until the 1500s, in fact, there was no b; the word was just "crum" or "cromme". Even Samuel Johnson gives "crum" as the first spelling in his 1755 dictionary.

What happened was that "crum" created a  derivative, "crummel", which then began to be pronounced "crumble" by analogy with words like "humble". This was a very common phonetic transformation; it happened also with "bramble" and "mumble", among others. Then the derivative influenced the root word, at least in spelling, though never in pronunciation.  Helped along by similar words like "lamb" (for the explanation of its silent "b", see this post), "comb", and "dumb", whose history was different, "crumb" actually beat out "crum", its final victory happening in the 19th century.

An interesting semantic development of the word "crumb" is "crumby" (also spelled "crummy", reflecting the earlier spelling of the root word). Why does "crummy" mean "of poor quality"?

In the 19th century, "crumb" started being used to mean "louse", and "crumby" meant "louse-infested". Just as we also use "lousy" to mean "inferior", "crumby" also took on this extended meaning.