The first aphorism of Bramha Sutra.

ATTHATHO BRAHMA JIJNASA --- Now this quest of the Truth or the Self or Brahman or the question of "Who Am I?" has arrived.
The word 'Brahman' has been derived from the root word (dhatu) 'Briha'. Brahman means the Self. The word self is derived from that dhathu. In Sanskrit root word is called dhathu. From briha dhathu. Every word in Sanskrit has come from a root. Like ‘Ram’ came from a root. When Ram was born he didn't have a name. His father brought Him to the sages to name him. When the sages saw that little child, they saw that he is attracting them in such a level that the sages feel the presence of that child in their mind. While they feel the presence of that child in their mind they get connected with the lord. So this child is a medium to connect with that infinite lord. This wonder child is the one whom the yogis can meditate upon spontaneously and that is why that child was named as RAM - “Ramanthi yogina yasmin sa Ram”, the one in whom the sages meditate and take refuse is RAM. Krishna was born and in the same way the sages came and they saw that the boy was attracting them towards him. The one quality of the God is attraction. The world also attracts us but there is a sense of dis satisfaction and extreme desire and unfulfillment. But with the attraction of God, we find peace and bliss and a natural flow of renunciation and fulfillment. We will see when we are meditating and are moving towards the self, the vibrations of the mind is very less we feel the attraction coming from inside. Like somebody is attracting from inside. Who is that? That is the Self. So when sages came to name Krishna they saw that Krishna is attracting them and that is why they named Krishna as “Ya karshathi sa Krishna”. Krishna has came from the word karshathi from "Krish" dhathu or the root word. In the same way Brahman came from the root ‘Briha’. Brahman doesn’t mean that somebody sitting in the heaven. Brahman means ‘Me, You, Everybody and my Self’. Briha denotes greatness to an infinite degree and therefore applicable to all objects which have the quality of greatness. But aptly to that object by nature and quality posses this greatness to an infinite degree. Hence the word Brahman primarily denotes that supreme person who is the abode of all auspicious qualities to an infinite degree and who is free from all worldly taint. This supreme person is the only being, the knowledge of whose nature results in liberation. After knowing Brahman the person becomes the possessor of all divine qualities and that also to an infinite degree. 'Then' denotes the immediate sequence and therefore signifies that the antecedent fact necessarily leads to an inquiry into Brahman. The word then means now the quest for truth has started, so when it says that 'Now' means 'When?'- when everything of this worldly activities have been accomplished and now we approach into the highest level where we come close to the realize the self and become free.