Why does Li Er call Lao Tzu not Li Zi?

In ancient times, we often called the great sage So-and-so, such as confucian Kong Qiu, honored as Confucius, Mojia Mo zhai, honored as Mozi; and the founder of the Famous Taoists, we called Laozi, but people are obviously called Li Er, what is going on?

In fact, the title "Zi" was originally a first-class title of the Zhou Dynasty, and was also used to indicate the honorific title of the Secretary of State to which the Son of Heaven belonged, but in the Spring and Autumn Period and the Warring States Period, after everyone no longer had rules and regulations on etiquette, the word "Zi" was also extended to be used for the honorific title of some accomplished people.

Li Er was the founder of the Taoist school, and politically, Lao Tzu advocated the rule of doing nothing and teaching without saying a word; in terms of self-cultivation, he paid attention to the practice of being humble and solid and not arguing with others; when Lao Tzu left the Hangu Pass, he left a five-thousand-word book "Tao Te Ching", which was all-encompassing, explaining the changes in the universe with the Tao, and was a masterpiece of the nation, so it was also revered as "Son". In the Spring and Autumn Period, the common "Mandarin" in various countries was the "Luoyang Yayan" at that time, in the pronunciation of this language, "Li" and "Lao" were actually very similar, coupled with the fact that there was no advanced communication method at that time, closed communication made many contents rely on word of mouth, so it was originally called "Plum", and everyone passed it on to become "Lao Tzu".

But no matter what kind of name, Li Er handed us down his wisdom and philosophical ideas, when we are confused on the road of life, read more of the philosophy of the sages, read Lao Tzu's "Tao Te Ching", it will certainly be gained.