The word Durga (??????)(??????) literally means "impassable", "inaccessible", "invincible, unassailable". It is related to the word Durg (?????) which means "fortress, something difficult to access, attain or pass". According to Monier Monier-Williams, Durga is derived from the roots dur (difficult) and gam (pass, go through). According to Alain Daniélou, Durga means "beyond reach".

The word Durga, and related terms appear in the Vedic literature, such as in the Rigveda hymns 4.28, 5.34, 8.27, 8.47, 8.93 and 10.127, and in sections 10.1 and 12.4 of the Atharvaveda. A deity named Durgi appears in section 10.1.7 of the Taittiriya Aranyaka. While the Vedic literature uses the word Durga, the description therein lacks the legendary details about her that is found in later Hindu literature.

The word is also found in ancient post-Vedic Sanskrit texts such as in section 2.451 of the Mahabharata and section 4.27.16 of the Ramayana. These usages are in different contexts. For example, Durg is the name of an Asura who had become invincible to gods, and Durga is the goddess who intervenes and slays him. Durga and its derivatives are found in sections 4.1.99 and 6.3.63 of the Ashtadhyayi by P??ini, the ancient Sanskrit grammarian, and in the commentary of Nirukta by Yaska. Durga as a demon-slaying goddess was likely well established by the time the classic Hindu text called Devi Mahatmya was composed, which scholars variously estimate to between 400 and 600 CE. The Devi Mahatmya and other mythologies describe the nature of demonic forces symbolised by Mahishasura as shape-shifting and adapting in nature, form and strategy to create difficulties and achieve their evil ends, while Durga calmly understands and counters the evil in order to achieve her solemn goals.

There are many epithets for Durga in Shaktism and her nine appellations are (Navadurga): Shailaputri, Brahmacharini, Chandraghanta, Kushmanda, Skandamata, Katyayini, Kaalratri, Mahagauri and Siddhidatri. A list of 108 names of the goddess are recited in order to worship her and is popularly known as the "Ashtottarshat Namavali of Goddess Durga".

One of the earliest evidence of reverence for Devi – the feminine nature of God, appears in chapter 10.125 of the Rig Veda, one of the scriptures of Hinduism. This hymn is also called the Devi Suktam hymn (abridged):

I am the Queen, the gatherer-up of treasures, most thoughtful, first of those who merit worship.
     Thus gods have established me in many places with many homes to enter and abide in.
Through me alone all eat the food that feeds them, – each man who sees, breathes, hears the word outspoken.
     They know it not, yet I reside in the essence of the Universe. Hear, one and all, the truth as I declare it.
I, verily, myself announce and utter the word that gods and men alike shall welcome.
     I make the man I love exceeding mighty, make him nourished, a sage, and one who knows Brahman.
I bend the bow for Rudra , that his arrow may strike, and slay the hater of devotion.
     I rouse and order battle for the people, I created Earth and Heaven and reside as their Inner Controller.
On the world's summit I bring forth sky the Father: my home is in the waters, in the ocean as Mother.
     Thence I pervade all existing creatures, as their Inner Supreme Self, and manifest them with my body.
I created all worlds at my will, without any higher being, and permeate and dwell within them.
     The eternal and infinite consciousness is I, it is my greatness dwelling in everything.

– Devi Sukta, Rigveda 10.125.3 – 10.125.8,

Devi's epithets synonymous with Durga appear in Upanishadic literature, such as Kali in verse 1.2.4 of the Mundaka Upanishad dated to about the 5th century BCE. This single mention describes Kali as "terrible yet swift as thought", very red and smoky colored manifestation of the divine with a fire-like flickering tongue, before the text begins presenting its thesis that one must seek self-knowledge and the knowledge of the eternal Brahman.

Durga, in her various forms, appears as an independent deity in the Epics period of ancient India, that is the centuries around the start of the common era. Both Yudhisthira and Arjuna characters of the Mahabharata invoke hymns to Durga. She appears in Harivamsa in the form of Vishnu's eulogy, and in Pradyumna prayer. Various Puranas from the early to late 1st millennium CE dedicate chapters of inconsistent mythologies associated with Durga. Of these, the Markandeya Purana and the Devi-Bhagavata Purana are the most significant texts on Durga. The Devi Upanishad and other Shakta Upanishads, mostly dated to have been composed in or after the 9th century, present the philosophical and mystical speculations related to Durga as Devi and other epithets, identifying her to be the same as the Brahman and Atman (self, soul).

Origins

The historian Ramaprasad Chanda stated in 1916 that Durga evolved over time in the Indian subcontinent. A primitive form of Durga, according to Chanda, was the result of "syncretism of a mountain-goddess worshiped by the dwellers of the Himalaya and the Vindhyas", a deity of the Abhiras conceptualized as a war-goddess. Durga then transformed into Kali as the personification of the all-destroying time, while aspects of her emerged as the primordial energy (Adya Sakti) integrated into the samsara (cycle of rebirths) concept and this idea was built on the foundation of the Vedic religion, mythology and philosophy.

Epigraphical evidence indicates that regardless of her origins, Durga is an ancient goddess. The 6th-century CE inscriptions in early Siddhamatrika script, such as at the Nagarjuni hill cave during the Maukhari era, already mention the legend of her victory over Mahishasura (buffalo-hybrid demon).

Birth

Durga was born with the power of the 3 gods Brahma,Vishnu and Shiva to defeat the Asura Mahishasura

European traders and colonial era references

Some early European accounts refer to a deity known as Deumus, Demus or Deumo. Western (Portuguese) sailors first came face to face with the murti of Deumus at Calicut on the Malabar Coast and they concluded it to be the deity of Calicut. Deumus is sometimes interpreted as an aspect of Durga in Hindu mythology and sometimes as deva. It is described that the ruler of Calicut (Zamorin) had a murti of Deumus in his temple inside his royal palace.^[44]