The "Yeos" referred to in Boolavogue are the locally raised Yeomanry regiments (normally cavalry units).
During the French Revolutionary War and the Napoleonic War militia regiments were raised for local/home defence. Infantry were referred to as Volunteers and cavalry as Yeomanry regiments. Men serving in these units could not be used on foreign service. Another raised primarily for home defence at that time were called Fencibles - they could be used as reserves for the regular army.