GIREESHA

Shiva is called as Gireesha because he is the proprietor of Kailash mountain. Shiva is very much fond of highlands. Therefore he keeps on dwelling in the mountains. Just by keeping a distance from social disturbances, he is always exploring into the field of meditation.
If the conjunction of this word is supposed to be ‘gir’ and ‘isha’, then ‘gir’ means the speech and ‘isha’ means one who controls. Shiva is the only controller of all through divine speech of the Vedas. With the same expression, Acharya Bhaskar sings the glory of this name—

भूरिगणे पदवाक्ये निष्कलुषे सुसमर्थः।
पर्वतराडपि शम्भो! तेन मतोऽसि गिरीशः॥

Purport: O Shambhu! You are king of all mountains and You are able to perfectly compose extremely excellent and spotless phrases in prescribed meters, so you are named as Gireesha.
There is a title namely ‘Giri’ among the ten titles of Dashnam Sanyasa order (monks). Lord Mahesh is known as Gireesha because he is worshipped by the monks of Giri order. In the spiritual science, Shankar is called Gireesha because he predominantly resides in the crown chakra. As Shiva is the master of physical form of Kailash mountain, similarly he is the Lord of spiritual Kailash too.
If Shiva is the director of mountains, then it shows that Himalya mountain is also an expansion of Shiva. That is not separated to Shiva. Serving faithfully the speech of Vedas and serving Vedic scholars is the true sense of worship of Gireesha.