An ochimusha is a samurai of a defeated army who survives and flees from the war. Some of them even created a village on mountain slopes and so on to where they had escaped. During the Sengoku Period (Period of Warring States), ochimusha were hunted by farmers who sought their belongings or reward in exchange for their head.
An idiomatic phrase "ochimusha are afraid of even a head of silver grass" means that you are afraid of anything when you are scared.
In some regions, such as Gifu and Nagano Prefectures, ochimusha are called 'daiko.'
The most widely accepted theory is that they were called 'dayu' (high steward) at first and then it changed in these regions.