The Iroquoian language family is named after the Iroquois Confederacy that included the Mohawk, Onondaga, Oneida,Cayuga, and Seneca tribes.  The Confederacy, founded in the latter part of the 16th century in what is now central New York State, came to be known as the League of Five Nations.  In the early part of the 18th century the Tuscarora, an Iroquoian people of present-day North Carolina, migrated to New York State and became part of the Iroquois Confederacy which then came to be known as Six Nations. The term Iroquois is thought to be derived from a derogatory Algonquian word which means ‘rattle snakes’. The Iroquois call themselves the Ho-de’-no-sau-nee ‘people of the longhouse’, because they traditionally lived in large longhouses which housed a social unit consisting of several families. [1]

References:

[1] About World Languages, “Iroquoian Language Family” by Irene Thompson.  Updated March 27, 2013 by Jon Phillips:  http://aboutworldlanguages.com/iroquoian-language-family