In the first years of the twentieth century heterosexual and homosexual were still obscure medical terms, not yet standard English. In the first 1901 edition of the "H" volume of the comprehensive Oxford English Dictionary, heterosexual and homosexual had not yet made it.
Neither had heterosexuality yet attained the status of normal. In 1901, Dorland's Medical Dictionary, published in Philadelphia, continued to define "Heterosexuality" as "Abnormal or perverted appetite toward the opposite sex."" Dorland's heterosexuality, a new "appetite," was clearly identified with an "opposite sex" hunger. But that craving was still aberrant. Dorland's calling heterosexuality "abnormal or perverted" is, according to the Oxford English Dictionary's first Supplement (1933), a "misapplied" definition. But contrary to the OED, Dorland's is a perfectly legitimate understanding of heterosexuality according to a procreative norm.
The twentieth century witnessed the decreasing legitimacy of that procreative imperative, and the increasing public acceptance of a new hetero pleasure principle. Gradually, heterosexuality came to refer to a normal other-sex sensuality free of any essential tie to procreation. But only in the mid- 1960s would heteroeroticism be distinguished completely from reproduction, and male-female pleasure sex justified for itself. ...
Between 1877 and 1920 Americans were embarked on The Search for Order, documented in historian Robert H. Wiebe's book of that title. Though Wiebe doesn't mention it, this hunt for regularity gave rise in the arena of sex to the new standard model heterosexuality. This paralleled early-twentieth-century moves to standardize railroad track widths, time zones, business and manufacturing procedures (discussed by Wiebe), as well as to test and regularize intelligence and femininity and masculinity....
In 1923, "heterosexuality" made its debut in Merriam Webster's authoritative New International Dictionary. "Homosexuality" had, surprisingly, made its debut fourteen years earlier, in 1909, defined as a medical term meaning "morbid sexual passion for one of the same sex." The advertising of a diseased homosexuality preceded the publicizing of a sick heterosexuality. For in 1923 Webster's defined "heterosexuality" as a "Med." term meaning "morbid sexual passion for one of the opposite sex." Only in 1934 does "heterosexuality" first appear in Webster's hefty Second Edition Unabridged defined in what is still the dominant modern mode. There, heterosexuality is finally a "manifestation of sexual passion for one of the opposite sex; normal sexuality." Heterosexuality had finally attained the status of norm.