ṬĪKĀ, derived from the root ṭīk, a loan word from the aboriginal languages, meaning 'to mark' or 'to explain', signifies commentary, exegesis or explanation, especially of a scriptural text. Originally meant to provide a simple paraphrase of the spiritual and mystical revelations, a ṭīkā may now embrace an exhaustive analysis and interpretation of the text. Such ṭīkās and commentaries have been part of the Indian religious tradition since ancient times. In tracing the history, reference is made to Yāska Munī (circa 700 BC) who mentions in his Nirukta numerous preceding commentators of the sacred scriptures. During AD 800 to 1500, a large number of ṭīkās were written on Bādarāyaṇa's Brahmasūtra and on the Bhāgavad-gītā by scholars holding different views and proffering different interpretations of the works. Every new interpretation of a text gave birth to a new school of thought which subsequently developed in some cases, into a new and independent sect. In the Sikh tradition, interpretation of the Gurūs' word and teaching had begun contemporaneously with them and among written works instances can be cited of the expository verse of Bhāī Gurdās (d.1636) and the prose discourses of Miharbān (1581-1640). The first regular ṭīkās to appear were those of the Udāsī sādhū Ānandghana who wrote during 1795-1802 commentaries of Japu, Āratī, Oaṅkār and Siddha Gosṭi. He was followed by Santokh Siṅgh (Garbgañjanī ṭīkā) and Tārā Siṅgh Narotam (Ṭīkā Gurū Bhāv Dīpikā). A major exegetical work was a commentary encompassing the entire Sikh Scripture, the Gurū Granth Sāhib, which was commissioned by Rājā Bikram Siṅgh, ruler of the princely state of Farīdkoṭ. The work completed in 1883 is popularly known as the Farīdkoṭ Ṭīkā. Two other full-scale ṭīkās of the Gurū Granth Sāhib are Srī Gurū Granth Sāhib Darpaṇ by Professor Sāhib Siṅgh and Srī Gurū Granth Sāhib Jī Saṭik by Giānī Bishan Siṅgh. Bhāī Vīr Siṅgh, the famous poet and savant, launched another ṭīkā of the Gurū Granth Sāhib, though he did not live to complete it. He had covered 607 pages of the original texts and his work has been published in seven volumes.