means an abundance of money, valuable possessions, or resources — and by extension any rich plenty of a thing.

from From the Middle English 'welthe,' built on Old English 'wela' (well-being, prosperity) — the same root that gives us 'weal' and 'well.' So the word originally meant not 'lots of stuff' but simply 'being well,' shaped on the pattern of 'health.' Riches were just one flavor of doing well; over time the money meaning crowded out the rest.