The term 'Sign of Holiness' is often associated with the four-letter word 'HALO'. A HALO is a symbol of holiness, divinity, and spiritual power that has been used in various religions for centuries. It is typically depicted as a circle of light around the head of a holy figure. In Christianity, it is often used to represent the presence of God or an angel. In other religions, it may be used to represent a divine being or a spiritual power.