Polygamy was lived secretly in the LDS church from about 1831 to 1852. The first mormon prophet had 20-30 wives and was murdered for practicing plural marriage privately while denying it publicly.

Polygamy was lived openly from 1852 to 1890 by the LDS church in Utah. The church made a show of abandoning the practice in order to get statehood. It wasn't until the second manifesto about 20 years later that the church started excommunicating new polygamists.  Since that time, the LDS church has taken a very harsh and intolerant stance against anyone who publicly admits that they practice polygamy, or claims that it should be practiced.. (Polygamy still happens among members of the LDS church, just so long as those practicing in it are discrete, but not a moment longer.)
When the church abandoned plural marriage with the second manifesto, existing polygamists were granted amnesty by the government, and were allowed by the church and the state to continue living polygamy until they died. The last practicing polygamist LDS prophet died in 1918.
http://www.absalom.com/mormon/polygamy/faq.htm

quote:

In 1999, Morning Glory Zell-Ravenheart was asked by the editor of the Oxford English Dictionary to provide a definition of the term (which the dictionary had not previously recognized). The words "polyamory/ous/ist" were formally added to the OED in 2006.[3]

quote:

ORIGINAL: SugarMyChurro

From wiki: http://en.wikipedia.org/wiki/Polyamory

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Terminology

Polyamory is a hybrid word: poly is Greek for many (or multiple) and amor is Latin for love. The word has been coined, seemingly independently, by several people, including Morning Glory Zell-Ravenheart, whose article "A Bouquet of Lovers" (1990) is widely cited as its source [2] (but see below), and Jennifer Wesp who created the Usenet newsgroup alt.polyamory in 1992. [5] However, the term has been reported in occasional use since the 1960s[citation needed], and even outside polygamous cultures such relationships existed well before the name was coined; for one example dating from the 1920s, see William Moulton Marston. There are no verifiable sources showing the word "polyamory" in common use until after alt.polyamory was created. The older term polyfidelity, a subset of polyamory, was coined decades earlier at Kerista.

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Lordandmaster:

Which version of the OED has that word listed? Mine doesn't have it...sadly...