Unbeknown (adverb)

1. Without one's knowledge or consent.
2. Without one's awareness.

Origin:

Late 16th century: from un- (expressing negation) + beknown, past participle of the archaic verb beknow.

Examples:

1. Unbeknown to her parents, she had been sneaking out at night.
2. He had been taking the medication unbeknown to his doctor.
3. The company had made changes unbeknown to the employees.
4. Unbeknown to her, he had been planning to propose.
5. Unbeknown to everyone, the company had been in financial trouble for months.