Indian file

Attested since the 18th century, as Native Americans traversed woods in this way.

Indian file

1. (especially US, uncommon) Single file.
   • 1791, Voyages And Travels Of An Indian Interpreter And Trader, page 69:

     In about an hour they returned very much intoxicated, singing their dead war songs, and every warrior naked, painted black from head to foot: as they approached the house in Indian file, each one repeated the following words […]

• Usually used as walk (march, approach, etc) Indian file (adverbially) or walk in Indian file. Until the 19th century, the form walk in an Indian file was sometimes encountered.