capacious

Capacious comes from Latin capāx, meaning "wide, spacious, large, capable," combined with the suffix -ious. It pushed out the native Old English word numol, which had covered similar ground.

The facts given don't trace a meaning shift beyond its Latin root — it entered English already carrying the sense of being wide or able to hold a lot, and simply replaced the older English term for that idea.

It shares its Latin root, capāx, with the idea of capability itself — both point back to something able to hold or contain much.