This is some information about tail. First two pieces are from our mythological literature.

Aanjaneya and His Tail
(1) When Aanjaneya went in search of Seetaa Jee to Lankaa, Lankaa's King Raavan asked his son meghnaad to arrest him to bring him to him to let him see that from where he had come. So when Hanumaan came in the court of Raavan, he did not offer a seat to him. This offended Hnaumaan, so he expanded his tail, rolled his tail around made a seat for himself, and sat over it.

(2) Later when Raavan got angry at him, he ordered his people to tie cloth on his tail, pouring oil on that cloth and set fire to it. Aanjaneya increased his tail so much that, it is said, that Lankaa's all cloth and oil was finished but Hanumaan's tail's end did not appear. Hanumaan then reduced his size and jumped over palaces and ran here and there and burnt the city and gardens of Lankaa. So this was the greatness of a tail.

(3) In Mahaabhaarat times, Aaanjaneya took the form of an old monkey and laid his tail across the way when Bheem was going in search of the Kalyaan Saugandhik flower asked by Draupadee. First Bheem did not recognize him and asked the monkey to move his tail aside so that he could pass the path. Since Bheem was very proud of his might, it was his insult that he should move a monkey's tail. But to make him understand that Aaanjaneya was his elder brother, he asked Bheem to move his tail from path and go if possible. In spite of Bheem's several requests when Hanumaan did not move his tail, Bheem had to move it himself. But what is this? Bheem, so mighty, could not even move the tail even a millimeter. Then he knew that he was not an ordinary monkey, so he requested him to show his real identity. Then Hanumaan showed him his real Roop (form) and said to him - "I am your elder brother."

Bheem could not reconcile this information and told him that his mother Kuntee did not tell him about any of his elder brother except Yudhishthir. Then Hanumaan explained him how he was Bheem's elder brother. After this they talked for a while and Bheem told him that they were to have a war with his cousins, so if he could help him to win him. Hanumaan told him that he would sit on Arjun's chariot's flag and guide that chariot move without any hindrance and see that flag from anywhere in the battlefield.

Saagar Manthan
During Saagar Manthan the Devtaa were holding the tail of Vaasuki Naag and Asur were holding the mouth side. If at all Vaasuki bite, let it go to Asuras.

Dog's Tail
(1) This is very old saying in Hindi "Kutte kee Poonch Baarah Baras Gaddhe mein dabaaee aur phir nikaalee to bhee tedhee kee tedhee." Means "we wanted to straighten the tail of a dog, so we kept it an a pit for 12 years, but when we took it our after 12 years, it was still crooked". Which means "It is futile trying to straighten dog's tail". The dog's tail is always crooked (a little bent). If at all we put it through a pipe for years, on removal from the pipe the tail will still be crooked. The saying is used to mention it is difficult to mend certain bad habits of people.

(2) Chaanakya has also remarked about it - "The tail of the dog serves no purpose. It does not cover the extrusion area or wagging no flees or insects get clear of. It cannot wag the tail sideways towards the body."

Nine Without a Tail
Very often when we have to talk of zero, we can mention it as "nine without a tail".

Valpar
Valpar is a place near Ooty. The hill from distance appears like a tail and its route is steep with many hair pin bends.

Tail Piece
Information written at the end of a big data is called as tail piece.

Lizard and Their Tail
The lizards when feel of danger may cut their own its tail and run. This self cutting process does not give any pain to lizard.

Calculating the Age of Animal
There is a method of seeing the age of animal counting the number of bones in the tail.

Specialty of Tail
Animals' tail is normally at the end of their backbone. It primarily covers their excretion area.
Many animals can wag their tail sideways which ward of the insects etc sitting on their bodies.
Tail is another sensitive area like horn and if you hold it, the animal may get irritated. Domesticated cows and oxen can be an exemption.
A tail has much more weight in comparison to its physical look and feeling.