"Bury the hatchet" is a common idiom used to describe an effort to resolve tension or come to peace with an enemy or foe. If two coworkers develop a conflict over a work-related issue, for instance, they might agree after a period of time to "bury the hatchet."
The use of this phrase to mean peaceful resolution stems from a 1749 peace agreement between Apache chiefs and Spaniards in San Antonio. A hatchet was one of several weapons laid on the ground as a display of peaceful commitment. Despite its more literal origins, this idiom is normally used in reference to resolution of emotional conflicts.