Brihadaranyaka Upanishad 1.38

आत्मैवेदमग्र आसीत् पुरुषविधः । सोऽनुवीक्ष्य नान्यदात्मनोऽपश्यत् । सोऽहमस्मीत्यग्रे व्याहरत् । ततो अहन्नामाभवत् ॥

atmaivedam agra asit purushavidhah | so'nuvikshya nanyad atmano'pashyat | so'ham asmity agre vyaharat | tato aham nama abhavat ||

In the beginning this was the Self alone, in the shape of a person. He looked around and saw nothing other than himself. He first said: 'I am He' (so'ham asmi). Therefore he came to be known as Aham (I). Hence even now, when addressed, one first says: 'It is I,' and then speaks whatever other name he has.

आरम्भ में यह आत्मा ही था, पुरुष के रूप में। उसने चारों ओर देखा — अपने अतिरिक्त कुछ नहीं दिखा। उसने पहले कहा: 'सोऽहम् अस्मि।' इससे 'अहम्' नाम हुआ। इसीलिए जब किसी को पुकारा जाता है, तो वह पहले 'मैं हूँ' कहता है, फिर अपना नाम।