Bury the hatchet
To settle your differences with an adversary.
The supposed language of Native Americans that we are familiar with is largely the invention of Hollywood scriptwriters - 'white man speak with forked tongue', 'kemo sabe' etc. The figurative expression 'burying the hatchet' is different in that it did originate as an American Indian tradition. Hatchets were buried by the chiefs of tribes when they came to a peace agreement.
Not just a B-movie plot device - hatchets really did get buried.
The phrase is recorded from the 17th century in English but the practice it refers to is much earlier, possibly pre-dating the European settlement of America. A translation of Thwaites' monumental work Jesuit Relations, 1644, suggests the practice:
"Proclaim that they wish to unite all the nations of the earth and to hurl the hatchet so far into the depths of the earth that it shall never again be seen in the future."
The New England Historical & Genealogical Register for 1870 has a record that Samuel Sewall made in 1680, where he recounts the burying of hatchets by Native American tribes:
"Meeting wth ye Sachem [the tribal leaders] the[y] came to an agreemt and buried two Axes in ye Ground; which ceremony to them is more significant & binding than all Articles of Peace the Hatchet being a principal weapon wth ym."
References in print that explicitly mention 'burying the hatchet' are somewhat later. The History of the Five Indian Nations of Canada, 1747, by the splendidly named Cadwallader Golden, Esq., is the earliest I've found:
"The great Matter under Consideration with the Brethren is, how to strengthen themselves, and weaken their Enemy. My Opinion is, that the Brethren should fend Messengers to the Utawawas, Twibtwies, and the farther Indians, and to send back likewise some of the Prisoners of these Nations, if you have any left to bury the Hatchet, and to make a Covenant-chain, that they may put away all the French that are among them."
See other phrases that were coined in the USA.