Definition of Festing man
In old English law, a bondsman; a surety; a frank-pledge, or one who was surety for the good behavior of another. Monasteries enjoyed the privilege of being "free from festing-men,” which means that they were "not bound for any man’s forthcoming who should transgress the law.” See Frank-pledge.
That's the definition of Festing man in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.