Final answer:
Giving small, unexpected gifts to fill someone else's bucket is an example of the Bucket-Filling Principle from the book 'How Full Is Your Bucket'.
Step-by-step explanation:
According to the authors of How Full Is Your Bucket, giving small, unexpected gifts to fill someone else's bucket is an example of the Bucket-Filling Principle.
The authors explain that this principle is about doing kind actions and saying positive words to make others' lives better. By giving small, unexpected gifts, we can make someone feel appreciated and valued, which fills their emotional bucket.