The term "better half" is a colloquial expression used to refer to someone's spouse or partner, typically in a loving or affectionate manner. It suggests that this person is the more virtuous or admirable part of a couple, indicating that they complement each other well.
The phrase "better half" is believed to have originated in the late 18th century and reflects a traditional view of marriage, where one partner is often considered to be the more virtuous or commendable of the two. The phrase draws on the idea of partnership, suggesting that each partner brings distinct qualities that enhance their union.