The use of the phrase “better half,” in English, generally applies to the speaker's spouse or partner, and is used both to complement the spouse, and as an expression of humbleness and honor by the speaker. Although the meaning of this idiomatic phrase does not vary too much, language historians have identified different significances and traditions behind its use through many centuries.
One of the implications of this common phrase is in the adjoining of marital partners. This reflects some of the traditional parts of wedding vows in many English-speaking countries, for example, when a wedding officiant may say “what God has joined, let no man put asunder.” Here, the two people essentially become “halves” of one another.
To further illustrate the use of this phrase, readers can contrast it with negative idioms around marriage, such as “ball and chain,” which are often used in jest, but have a literally negative connotation. By contrast, the use of the phrase “better half” implies humility and admiration on the part of the speaker or writer. It is a generous attribution to the other person in the couple.
Historians point out that in some original contexts, the term “better half” was used, not for a marriage partner, but for a valued or treasured friend. Here, the general phrase often indicated a philosophical valuation, such as a relationship between two friends who frequently argued or discussed philosophy or other profound topics. Over time, the phrase became almost exclusively applied to those who are married, engaged in civil partnerships, or in common law marriage. The versatility of this phrase leaves it open to changing uses consistent with societal changes and trends.
The phrase “better half” can also have a generally chivalrous context. Some might see it as related to another popular phrase in historic English: “the fairer sex.” Where the phrase “my better half” may be more frequently used by men to indicate women, it correlates with the idea that women are a favored gender in some ways, or display more positive characteristics than men as a whole. This is not necessarily a part of the meaning of the phrase “better half,” but can be seen as part of its implied historic use; indeed, even today it would be unusual, if not unheard of, for a wife to use the phrase in regard to her husband.