A more thorough explanation:

Definition: Affiance (pronounced uh-fahy-uhns) is an old-fashioned word that has two meanings:

1. The act of confiding in someone.
2. The act of promising to marry someone.

Examples:

• She affianced her deepest secrets to her best friend.
• He affianced himself to his childhood sweetheart.

The first example shows how affiance can mean confiding in someone. The woman in the example trusts her best friend enough to share her deepest secrets with her. The second example shows how affiance can mean promising to marry someone. The man in the example has pledged his love and commitment to his childhood sweetheart.