Meaning:
The phrase a snake in one's bosom refers to a person whom one has treated well and taken care of but turned out to be traitorous, untrustworthy, or ungrateful.
Examples:
- I had taken him into my care, but when he grew up, he stole all my money and fled away. I had nourished a snake in my bosom.
- He loved her so much and treated her like a queen. But, after ten years of marriage, he found out that he had cherished a snake in his bosom. She run off with a younger man.