As titles of some Acharyas, the word 'Desika' or 'Desikan' are used.What is the meaning of this word according to the scriptures?
According to Tantric scriptures, Deshika is used to denote the Guru, who is capable of doing Anugraha towards the disciple.
A formal definition is as follows:
KarunAmaya-murtitvA-deshikah kathitah priye ||
Because he wears the form of the deity, devata, because he bestows grace on the disciple, shishya, and because he is the embodiment of compassion, karuna, he is called Deshika.
KulArnava Tantram 17.14
The word is used at many places of the mentioned Tantra text to denote the Guru.
Desika means an acharya or an expert teacher. It literally means who shows correct direction (who shows Disha (direction) to someone) or a guide. A guide guides is in the right path to reach our destination. Similarly in spiritual context, a deshika (guru) he shows direction to his disciples through his teachings and much more. A guru gives us mantra diksha and guides the disciple's way towards salvation. Hence guru is also called a Deshika.
See Importance of Guru (गुरु) in our daily Life as well as in Spiritual Life?. It has been used in many stotras and even in the Mahabharata. The word ends with 'n' or 'r' in Tamil. It means a teacher or a spiritual master. Words ending with 'r' shows respect whereas ending with 'n' is a normal way of calling a person. Generally, someone like a master is given respect and words end with 'r'.
Deśika m. a Guru or spiritual teacher, MBh. ; AgP. [ID=96585]
Garuda Purana Purva khanda chapter 48 deals with the installation of idols in temple. The first shloka is as follows.
pratiṣṭhāṃ sarvadevānāṃ saṃkṣepeṇa vadāmyaham /
sutithyādau suramyāṃ ca pratiṣṭhāṃ kārayedguruḥ // 1.48.1
Sūta said 1. I shall now succinctly explain the mode of installation of the idols of deities On an auspicious day, the preceptor shall perform the installation rites.
Later in the same chapter, many words synonymous to Guru are used like Acharya.
ācāryāḥ kecidicchanti jātakarmādyanantaram / (72.1)
pavitraṃ tu tataḥ kṛtvā kuryādājyasya saṃskṛtim // (72.2)
- Some preceptors maintain that installation of fire than be after Jātakarmas (the rite consequent to the birth of a child). Wearing Pavitra, the Ājya (ghee) shall be consecrated.
Similarly, the word deshika is also used.
evaṃ homavidhiṃ kṛtvā nyasenmantrāṃstu deśikaḥ / (86.1)
caraṇāv agnim īḍe tu iṣe tvo gulphayoḥ sthitāḥ // (86.2)
- Having thus performed the rite of Homa, the preceptor shall perform mantra-nyāsa :—at the feet with Agni mile mantra at the ankles with Iṣe tvā mantra.
It is used as synonym for "Acharya" even in real life. For Example, Sri Vaishnava Acharya Vedanta Desikan got his name because he was bestowed the title Vedanta Acharya. Following is his invocatory prayer (Taniyan).
Shriman Venkatnarthaye Kavitakirkakesari
Vedantacharyavaryo me Sannidhatam sada Hradi |
It is believed that Sri Ranganatha inferred the title Vedantacharya or Vedanta Desika to Sri Vaishnava Acharya Venkatanatha.