영어로 "a snake in one's bosom"의 정의와 의미

I thought our love was not only mutual but indestructible; and yet, I have nursed a snake in my bosom all these years: my darling husband has cast me out and run off with a younger woman.

I thought the profligate had seen the light and was seeking redemption, and so I took him into my care. But before long, I knew I had nurtured a snake in my bosom, as I awoke one morning to find myself robbed blind!