It's an old-fashioned word now, but a handmaiden was once a servant who worked for a wealthy family. You might feel like a handmaiden when your parents tell you to scrub every bathroom in the house.
Long ago, a handmaiden (also called a handmaid) often served as the personal servant or maid to the lady of the house. You're much more likely to encounter this word in a book or movie these days, since someone employed in a home is more likely to be called an assistant, a housekeeper, or a cleaner. The term handmaiden comes from the sense of being "close at hand."