So the phrase 天上天下唯我独尊 was (supposedly) originally uttered by Siddhartha Gautama when he was born (the OG Buddha). After his birth, it is said he walked 7 steps. Under each footstep bloomed a lotus flower and stopping before taking the eight step, he proclaimed that "In the heavens and on the Earth, I am the only one to be revered". The seven steps signify the steps to enlightenment and his comment was made to declare that he was the one that would reach enlightenment (which, spoiler alert, he does). In modern usage, however, its often has a more negative connotation or at least less holy connotation to it, instead used to show unbridled arrogance or egotism.

Hence, fitting for our Tenryuu-sama

vietknight243 said:

So the phrase 天上天下唯我独尊 was (supposedly) originally uttered by Siddhartha Gautama when he was born (the OG Buddha). After his birth, it is said he walked 7 steps...

Of note is the "birth" is an embellishment - a sort of parable (is that the right word?) about the moment that the Buddha has reached enlightenment (thus, birth of "Buddha" from "Siddhartha" that no longer exists). So, yes, it really does give that kind of impression for someone who is decidedly not a person who has just attained enlightenment.

vietknight243 said:

So the phrase 天上天下唯我独尊 was (supposedly) originally uttered by Siddhartha Gautama when he was born (the OG Buddha). After his birth, it is said he walked 7 steps. Under each footstep bloomed a lotus flower and stopping before taking the eight step, he proclaimed that "In the heavens and on the Earth, I am the only one to be revered". The seven steps signify the steps to enlightenment and his comment was made to declare that he was the one that would reach enlightenment (which, spoiler alert, he does). In modern usage, however, its often has a more negative connotation or at least less holy connotation to it, instead used to show unbridled arrogance or egotism.

Hence, fitting for our Tenryuu-sama

Wow. That is extremely egotistical. No wonder it has such a negative connotation to it.

Andyoats said:

Wow. That is extremely egotistical. No wonder it has such a negative connotation to it.

The original (supposed) line(s) was "Aggo 'ham asmi lokassa, jettho 'ham asmi lokassa, settho 'ham asmi lokassa", as recorded in the Pali canon. Or, literally, "I am the first in the world. I am the eldest in the world. I am the best in the world."

Still sounds egostical, but this is then followed by:

"Ayam antima jati, natthi dani punabbhavo."

Or "This is my last rebirth. There is no more becoming for me."

So from context it's again one of those mindfu— mindbending "Self is not self" kind of thing.

As for 独尊, it could be from a possible translation of "Aggo", since it can also mean "preeminent". Or they decided to roll aggo/jettho/settho into one word.