What is the story and principle behind adding the word "shree" श्री. Before our sacred religious books like "Shreemad Bhagvat श्रीमद भागवत " , Shreemad Bhagvad Gita श्रीमद भगवदगीता" etc. When was this tradiation born.?
Lord Shiva says in KulArnava Tantram that Sri should always be added at the start while addressing Gurus, Shastras and the Holy places.
SriGurum KulashAstrAni PujyasthAnAni YAni cha ||
BhaktyA Sripurvakam Devi Pranamya Parikirtayeth||
KulArnava Tantram, Chapter 11, Verse 43.
Hey Devi, Guru, Kula Shastras and Pujyasthana ( holy places or places that are worthy of worship ) --- while addressing any of these three the word "Sri" should be added at the start and they should be addressed only after prostrating before them with devotion.
Therefore, instead of mentioning simply KulArnava Tantram, one should say Sri KulArnava Tantram. Similarly one should say Sri KAshi Kshetra instead of simply KAshi and similarly for Gurus.
So, that's why there is a custom of adding Sri at the beginning of Holy Texts (scriptures).
Jaya Nitai! I know a partial answer to your question, and I will try and share all I know. This is what I was taught by my superiors. So the traditional meaning of the word श्री, is that it is a name of Maha-Lakshmi, the Goddess of fortune and prosperity. We see that this link is quite old (due to the presence of the Sri Suktam in the Rg Veda). Now, according to Puranic literature, Lakshmi (Sri) is the eternal consort and associate of Bhagavan Vishnu. Since Lord Vishnu is always invoked with His consort (since they are never separated), Sri was added before any Name of Lord Vishnu and all things associated with Him (like Sri Rama, and even things like Srimad Bhagavatam). So when we say "Sri Rama" we are actually calling upon Lord Rama, and His consort Sri (In the form of Sita Devi). In a similar way, Srimad Bhagavat invokes Lord Krsna in the form of the Bhagavata Grantha (which is non-different from Him) and also His consort (who is Sri). Th Scriptures which describe Lord Vishnu are non-different from Him, and therefore it is appropriate to place Sri before it. Another meaning that can be taken is that those who read and study these scriptures, will get the blessing of Sri. It is very rare to actually see "Sri" placed before the names of gods like Lord Shiva, Lord Brahma etc.
As this usage became common, people began to use "Sri" as a title to mean "those blessed by Shri; i.e those who are spiritually wealthy, prosperous and auspicious". As a result, all those things related to Lord Vishnu (such as His devotees; the Vaishnavs etc) were also given the label of "Sri". In our tradition, many great personalities and Acharyas are respectfully given the title of "Sri", showing they are blessed with wealth and prosperity (not necessarily material, but spiritual). In the Bengali tradition, we use the slight modification of the word Sri, (Srila) to address our past acharyas.
So in conclusion, the title of "Sri" means Lakshmi and thus was used before the name of Lord Vishnu and His avatars. Later it became associated with all those related to Him, and then later the term became used vaguely to mean anything or anyone that is (spiritually) prosperous and wealthy.
Daso'mi Nitai Dasa