Why do 'I'm up for it' and 'I'm down for it' mean the same thing

Nervous Breakdown (Mental Health Crisis)

What does the expression 'I'm down for you' mean? - Quora

What does 'down in the holler' mean? - Quora

Why do Americans add the phrase 'go ahead and' to an announcement that they are going to do something, as in 'I'm going to go ahead and switch on…' rather than 'Im

What does I'm down mean? Does it mean I feel down? and what is I

What is the difference between saying 'I'm up for that' and 'I'm down for that' if someone asks if you want to do something? - Quora

How to use 'I'm up to'? What does this phrase mean - Quora

Roll Safe Think About It Meme - Imgflip

What is the meaning behind the similar expressions I'm up for it and I'm down for it? - Poe

What does 'How 'bout them apples' mean? - Quora

Meaning of I'M DOWN FOR IT and I'M UP FOR IT - A Short English Lesson with Subtitles

Meaning of I'M DOWN FOR IT and I'M UP FOR IT - A Short English Lesson with Subtitles

Qual é a diferença entre I'm down for it e I'm up for it ?

After someone didn't get the meaning of “I'm down”. And lemme tell you, the follow up text took a while. : r/suicidebywords