"Yoga" as it is known to the world is really "Yog". The compound word 'Yogasan' can be separated to form 'Yog' and 'asan'. It became popular as the short form 'Yoga'.The Sanskrut word 'yog' is derived from a root 'yuj',meaning to join, to unite or to attach your mind with your body. Yog is the union of body, mind, emotions and intellect. Yog is a physical, mental and spiritual discipline, whose goal is the attainment of a state of perfect spiritual insight and tranquility.
योगेन चित्तस्य पदेन वाचां। मलं शरीरस्य च वैद्यकेन॥
योऽपाकरोत्तं प्रवरं मुनीनां। पतञ्जलिं प्राञ्जलिरानतोऽस्मि॥
आबाहु पुरुषाकारं। शङ्खचक्रासि धारिणं॥
सहस्र शीरसं श्वेतं। प्रणमामि पतञ्जलिम्॥
Let us bow before the noblest of sages Patanjali, who gave yoga for serenity and sanctity of mind, grammar for clarity and purity of speech and medicine for perfection of health. Let us prostrate before Patanjali, an incarnation of Adisesa, whose upper body has a human form, whose arms hold a conch and a disc, and who is crowned by a thousand-headed cobra.
-translation from http://www.bksiyengar.com/modules/IYoga/sage.htm
At the end.....
ॐ – पूर्णमदः पूर्णमिदम् पूर्णात् पूर्णमुदच्यते
पूर्णस्य पूर्णमआदाय पूर्णमेवावशिष्यते
ॐ शान्तिः शान्तिः शान्तिः
That is whole; this is whole;
From that whole this whole came;
From that whole, this whole removed,
What remains is whole.