A lonko or lonco (from Mapudungun longko, literally "head"), is a chief of several Mapuche communities. These were often ulmen, the wealthier men in the lof. In wartime, lonkos of the various local rehue or the larger aillarehue would gather in a koyag or parliament and would elect a toqui to lead the warriors in battle. Lonco sometimes forms part of geographical names such as the city of Loncoche (English: "head of an important person").
References
Mapuche, Seeds of the Chilean Soul: An Exhibit at the Port of History Museum at Penn's Landing, Philadelphia, Pennsylvania, March 27-June 30, 1992. Museo Chileno de Arte Precolombino. 1992. p. 58. https://books.google.com/books?id=33LjAAAAMAAJ&q=lonko+OR+lonco+OR+longko+ulmen+mapuche ↩
Mapuche, Seeds of the Chilean Soul: An Exhibit at the Port of History Museum at Penn's Landing, Philadelphia, Pennsylvania, March 27-June 30, 1992. Museo Chileno de Arte Precolombino. 1992. p. 43. https://books.google.com/books?id=33LjAAAAMAAJ&q=lonko+OR+lonco+OR+longko+toki+mapuche ↩