Facebook has transformed its gender options setting to reflect almost fifty different genders and has also given users the option to use gender-neutral pronouns. These changes will initially apply to Facebook's 159 million monthly US users.

The move reflects the US's recognition of the transgender rights movement. American college students have started to use gender-neutral pronouns to refer to themselves in a move to promote gender neutrality. A survey last year by the Human Rights Campaign, one of the US's biggest LGBT rights groups, found that 10 percent of the 10,000 lesbian, gay, bisexual transgender youths surveyed used 'other' or wrote in their own gender terms.

The attempt to use gender-neutral or politically correct terms has gained steam over the past two decades. But some terms, however well-meaning, just don’t catch on. Here are some of them.

Zie, hir: Gender-neutral pronouns that can refer to both men and women. It’s popular among the genderqueers (a catch-all term for gender identities outside men and women) on the internet, but unheard of outside it.

Waitron: A gender-neutral term for waiter. First used in 1980, the word was initially used by science fiction writers to describe robot waiters and it seemed to have machine-like connotations. Instead, the word "waitstaff" has gained popularity.

Domestic engineer: A more professional sounding word for housewife. It was also used as the title of a book about an engineer who invented a device to make household cleaning tasks simpler, and whose manufacturer, Dyson, became the market leader for vacuum cleaners.

Ethnically homogeneous area: Officialese for ghetto, a term that was originally used in Venice to refer to the part of the city where Jews were segregated. In the 1960s, ghettos in which African-Americans lived became synonymous with poverty and crime, leading to the invention of this euphemism.

Visually challenging: This synonym for ugly proved to be too ugly to find widespread acceptance.