Īśāna has its roots in the word "ish" which means the invisible power that governs the universe. The wielder of this power is "Īśāna". It is synonymous with Ishwar which means 'The Lord'. In Hindu Scriptures this is a name given to Shiva. As per Hindu scriptures Shiva has 5 heads each denoting one of the 5 tattvas (elements) namely Fire, Earth, Air, Water and Ether (also called as Sky-element or aakash-tattva in sanskrit) that make up the universe. This 5th head of Shiva faces the upward direction, towards the sky.
Īśāna signifies the subtle ethereal form of Shiva that represents transcendental knowledge. This dimension is reinforced by Vaastu Shastra[1] which says that Ishanya-disha (northeastern direction) represents Prosperity and Knowledge. So Īśāna also has a symbolic meaning. In Hindu customs, North represents wealth and happiness while the East symbolizes knowledge and peace; Īśāna is a combination of both. It is also considered to be the name of the god of Vastu Śāstra. the Brahman splits into male(Parashiva) and female(Parasakti) and manifests as the universe. The parashiva has five aspects:- 1)Sadyojata-west-aspect that propagates manifest brahman-associated with brahma-represents earth. 2)Vamadeva-north-aspect that sustains manifest Brahman-associated with Vishnu-represents water 3)Aghora-south-aspect that rejuvenates manifest Brahman-associated with Rudra-represents fire 4)Tatpurusha-east-aspect that reveals-associates with Rishi,Muni,Jnani,yogi-represents air 5)Isana-internal-aspect that conceals-associated with all that exist-represents ether