As a northeast dialect, this word is usually used as another name for "buddy" and "friend", and similar evolved names include "Tiezi" and "Tiebuddy".
It means the same thing, saying that the relationship is close, firm and trustworthy. It shows that the relationship between friends is very good.
In winter, children in northeast Inner Mongolia lick iron railings, which stick when they lick them and can't be pulled down. Sticking your tongue to the iron railing will lead to bleeding and broken skin. This time is a test of friendship. If you have a good friend beside you to help you breathe, you can pull it down when it is hot.
The result is often that he is still insisting when breathing. On the streets of northeast China, pairs of children are glued to the iron railings, and their eyes are full of friendship and pain. This is why people in Northeast China call their friends Lao Tie, that is, they have good relations. We lick iron together and bleed together.
reference data
Lao Tie. Laotie [citation time 2017-12-19]