riches: an abundant store of value, whether material wealth or a lavish supply of some good thing
At its core this word names abundance, a full and overflowing store. In everyday use that store is money and possessions, so most often it simply means riches or wealth.
But the New Testament writers, and Paul above all, stretch the same word to describe how lavishly God gives. They speak of the riches of his grace, his glory, his goodness, and his wisdom: not money, but an inexhaustible supply of these things. The link between the two senses is the single idea of overflowing plenty. Whether the subject is a full treasury or the depth of God's kindness, the word pictures more than enough.
The two senses often carry opposite moral weight. Material riches are portrayed as a spiritual hazard that can choke faith and prove worthless in the end, while the riches of God are the surest and most desirable wealth of all.