to bud, sprout, or blossom; to burst into growth, and so to thrive
At its heart this word pictures new growth breaking out into the open: a bud opening, a plant flowering, a shoot pushing up. The blossom is the visible proof that hidden life is at work, which is why the word so often carries a note of vigor and promise.
From that plain picture the Bible reaches easily into figures of speech. A person, a nation, or even the wicked can be said to blossom, meaning they flourish and prosper for a season. The comparison is almost always spelled out with a plant, so the reader is meant to see a person thriving the way a healthy vine or lily does.
The same idea of something bursting out onto a surface is used for a very different subject: a skin disease breaking out and spreading over the body, or boils erupting on skin. Here the word keeps its core meaning, an outbreak that pushes into view, but the thing coming out is a sore rather than a flower. English still reaches for the word break out, the way we speak of a rash breaking out.