Lokâyata is also referred to as Cârvâka, Bârhaspatya, nâstika, haituka vâda, anvikshiki, asura, etc. Haituka vâda means rationalistic/logical doctrines, which is the same as Anvikshiki. Asura, pâsândin, etc., were simply derogatory terms applied to Lokâyata and other heretical doctrines by writers from other affiliations. The key names of nâstika, Lokâyata, Bârhaspatya and Cârvâka are briefly explained below.
According to Pânini 4.460, the word nâstika is irregularly formed. Pâtanjali when commenting on this rule, explains âstika as one who thinks “it exists” and nâstika as one who thinks “it does not exist”. Jayâditya in his commentary on this sūtra, defines âstika as one who believes in other worlds (para loka) and nâstika as one who does not believe in other worlds. Manu Smriti defines âstika as one who rejects the Veda (nâstiko veda nindakah). Though, Manu’s definition would also apply to other heretical doctrines such as Buddhism and Jainism, his commentator Medathiti, explicity identifies them with Lokâyata. Nâstika is also defined as a godless person, which becomes the most common usage of the term in later times. Lokâyata is the only doctrine that meets all three definitions of Nâstika.
The origins and the exact meaning of the term Lokâyata are lost in obscurity, just like Sânkhya. The earliest reference to Lokâyata may possibly be its mention (grouped with Sânkhya and Yoga) in the Arthaśâstra (3rd century BCE) as a type of Anvikshiki (logical doctrine). Pâtanjali’s Mahâbhâshya (2nd century BCE) mentions Bhâguri as a Lokâyata author. The name Lokâyata appears in some Pâli texts – the Buddhist Pitakas – without ever being defined. The Amarakośa simple mentions the word without defining it and says it should be in the neuter gender as Lokâyatam. From these early references, it is impossible to determine what the name meant, except that it was a system comparable to Sânkhya and Yoga, in that the three formed a group of logical systems, while the Trayi (Veda) which was based on scriptural authority. None of these sources connect the name Lokâyata with Bṛhaspati, nor do any of the various Nâstika doctrines of this time, carry this appellation.
Lokâyata is made up of two words, of which the first word Loka is clear. The second work is ambiguous and can be read in different ways. According to the Aggavamsa (12th Century CE), the word may mean “to make effort” or “cease to make effort”. According to Budhaghosha (5th Century CE) in his Sâratta Pakâsini, it means the basis of the foolish and profane world. Dasgupta remarks that there may be two Lokâyata words – one indicating the Darsana which was primarily sophistry and the other as the adjective “prevalent among common people” (read as lokesu + âyata).Its meaning becomes clearer from texts dated to a few hundred years later when it is explicitly identified with atheistic doctrines, synonymous with Cârvâka and as the doctrine of Bṛhaspati. Based on this contextual evidence, Lokâyata is interpreted to mean “of the world” or “grounded in the real world” to mean it focused on this world and not on other worlds – which set it apart from all other doctrines and the Veda as afterlife and the existence of other worlds like Pitru loka formed crucial elements of these systems.
This means the philosophy or system of Bṛhaspati. It is likely that there were multiple Bṛhaspatis who have attained posterity though their works. However, from available references when Bṛhaspati’s name appears in the context of Nâstika systems, it appears to be a single individual who presumably was an early exponent of Nastika principles – gathering enough acclaim to find a mention in the Maitrayani Upanishad as one who spread false teachings and in the Taittiriya Brâhmana as splitting Gâyatri’s head, but she stayed alive, which may be interpreted as a symbolic description of his rejection of the Veda. He has been identified as Bṛhaspati, the perceptor of the devas – not unusual in Indian history where several authors of the same name have their works mixed up as in the case of Pâtanjali, Vâtsyâyana and others. By the 9th Century CE, Bârhaspatya was synonymous with Lokâyata and Cârvâka. It is noteworthy that by this time, a number of different heretic doctrines, possibly all of independent origins, yet having the common substratum of skepticism, were all integrated into Bṛhaspati’s doctrine. People who espoused such rational views were labeled followers of Bṛhaspati, though in truth, it is unlikely that they considered themselves to be followers of anyone.
Unlike Lokâyata, the name Cârvâka does not trace back to antiquity. The oldest known reference is in the Mahabharata (8th Century BCE to 5th Century CE). However, Cârvâka here is not a clear reference to a person affiliated to a nâstika school. Unambigious usage of this name for Bṛhaspati’s nâstika doctrine is known only from the 8th century CE, used by Jayantha, Haribhadra, Kamalasila, etc. By this time, the identity among the three names of Cârvâka, Lokâyata and Bârhaspatya is established. A few hundred years later, Gunaratna when commenting on Haribhadra, provides his understanding of these terms. However, as these names existed least a thousand years before his time, his etymology cannot be accepted with certainity.
They are called Cârvâka because they chew/eat. The word is irregularly formed (nipâtana) by a rule of the Unâdi section of the Siddhahaima (grammar). The word Loka means ordinary people who act without discretion and since the Cârvâkas do the same, they are also called Lokâyatas or Laukâyatikas. As they subscribe to the views of Bṛhaspati, they are called Bârhaspatyas – Gunaratna
Some scholars have written that Caru was a synonym of Bṛhaspati. Some others have interpreted Cârvâka as “sweet talker”, presumably to mean a smooth talking sophist. Some believe Bṛhaspati passed on his teaching to Cârvâka. Thus, we have multiple possible meanings for the term.