Chaulam is also called Cūḍākarma (चूडाकर्म) and Cūḍākaraṇam ((चूडाकरणम्) Chudakarana). Cūḍā means tuft (of hair) that is kept on the back side of the head while the remaining part is clean shaven. In tradition it is popularly called “Śikhā”. In Sanskrit the letters “ल (la)” and “ड (ḍa)” are often interchanged. So Caula (चौल) and Cūḍā (चूडा) mean the same. The Saṃskāra for which the purpose is making a “Cūḍā” (tuft / Śikhā) is called Caulam (चौलम्), and also Cauḷam (चौळम्).

Cutting the hair and keeping the head clean was one of the primary reasons to have a shikha; the process for which later on came to be regarded as an important event in the life of an individual. To keep the head clean some device was bound to be invented. Chopping the hair by means of an iron instrument was the natural course but people were also afraid of cutting and injuring themselves in this process. Necessity and fear both mingled together and gave rise to the Chudakarana ceremonies.

Almost all the mantras that are used in the Grhyasutras at the tonsure ceremony are found in the Vedic literature and they are all of specific character which shows that they were composed for the purpose of cutting the hair only. 

Atharvaveda has a short three mantra sukta dedicated to the tonsure ceremony. Wetting the head and invoking deities are the important rites mentioned in it. 

आयमगन्त्सविता क्षुरेणोष्णेन वाय उदकेनेहि । आदित्या रुद्रा वसव उन्दन्तु सचेतसः सोमस्य राज्ञो वपत प्रचेतसः

॥१॥ (Atha. Veda. 6.68.1)

This diligent barber, Savita, has come with the razor. O man, come fast with water. Let brilliant, wise and noble people with love at heart bless the child with holy water. O men of love and peace with the generosity of soma, join at the shining child’s tonsure ceremony.

अदितिः श्मश्रु वपत्वाप उन्दन्तु वर्चसा । चिकित्सतु प्रजापतिर्दीर्घायुत्वाय चक्षसे ॥२॥

Meaning: Let the razor cut the hair. Let water consecrate the child with brilliance. Let Prajapati enlighten the child and bless him to have a long age of good health, knowledge and holy vision.

येनावपत्सविता क्षुरेण सोमस्य राज्ञो वरुणस्य विद्वान् । तेन ब्रह्माणो वपतेदमस्य गोमान् अश्ववान् अयमस्तु प्रजावान् ॥३॥

Meaning: By the process the expert barber has shaved the head of the shining, loving and intelligent child with the razor, by the same ceremonial process, O Brahmanas, pray complete the tonsure ceremony of the child. May this child be rich in lands, cows and horses and may he have a noble family.

ज्योतिषाम् अपि तज् ज्योतिस् तमसः परम् उच्यते । 
ज्ञानं ज्ञेयं ज्ञान-गम्यं हृदि सर्वस्य धिष्ठितम् ॥ १८ ॥

jyotiṣām api taj jyotis tamasaḥ param ucyate |
jñānaṃ jñeyaṃ jñāna-gamyaṃ hṛdi sarvasya dhiṣṭhitam || 18 ||

Srimad Bhagavad Gita

The Self is the source of all light. The Self is beyond the darkness of matter and is unmanifested. The Self is knowledge, the Self is the object of knowledge, and the Self is the goal of knowledge. The Self is situated within you.