Shiva is known as Vamdeva because he enlightens all by the light of knowledge. The light of Shiva is extremely elegant and auspicious. It is never unbearable in spite of it’s sharp effulgence. All material elements born out of nature borrow light from others but Lord Vamdeva shines out of his inherent divine effulgence. Vedic dictionary has many meaning for ‘Vam’ and ‘Deva’. Vam means beautiful and attractive and Deva means one who glitters with paramount light. The grace of light is appreciated only then when it is self-manifesting. Shiva’s light does not depend on any outer source because he is the supreme spirit self. Suta Samhita exclusively elaborates it in these words—

जडं हि गम्यतेऽन्येन नाऽजडं मुनि पुंगवाः।
शिवो नैव जडः साक्षात् स्वप्रकाशैकलक्षणः॥

The inert is always known by others because it has no self-knowledge. Being transcendental to inert matter Shiva is soul power and thus he is self-illuminating. Bhaskar Roy describes this name very sweetly—

वामार्धेन क्रीडसि त्वं त्रिलोकीवक्राचारो वल्गुमोदोऽसि तस्मात्।
विश्वोत्तीर्णः स्त्रष्टृतामाप्यतीतः प्रेयानात्मा कथ्यसे वामदेवः॥

Your plays are performed by your divine potency which always stay on your left side and thus you stay aloof by the faults of creation. You are beyond this world because your behavior is opposite to the conduct of three worlds. You are exclusively blissful, hence you are called Vamdeva. Cultivating spiritual knowledge for self realization by subduing the powerful ignorance; this is the true form of worship of Lord Vamdeva.