Mother lode

When I saw the phrase mother lode, I realized that I hadn't seen it before. For some reason, I thought "lode" would be "load", that it was one word rather than two, and that the meaning implied "huge". Instead, it means "the principal vein or lode of a region" and "a principal source or supply."

Actually, "lode" is an odd word. It's cute, but it's also has a clumsiness about it. Like "lobe".