In short: “ish” is a slang term used to replace the word “sh*t” in lyrics, on merchandise, etc.
Several months ago, I wrote about The Usos wearing shirts, sweatshirts, etc. with the phrase “Texas since day one ish” on them. The Usos have adopted this “day one ish” phrase as their slogan and have included in their music. But the questions remains, what does “day one ish” mean?
The most likely interpretation for most people is the most common use of the term “ish”: as a slang term to replace the word sh*t.
The Usos have been mostly quiet on the topic, even with a large majority of people questioning it weekly. Back when Talking Smack would air after Smackdown Live, Jimmy Uso was quoted as saying it means, “sort of day one…like it’s almost two.” However, no one else on the panel agreed with this. He likely said this because he can’t say what the real origin is (you know, for the kids).
More recently, the phrase has been adjusted to be “down since day one ish” rather than just “day one ish.” So, maybe for them it does mean that they have been down since “almost day one.” But, it could still be meant as the previous definition. The Usos have been working, day in and day out. They’ve been down, in the grind, doing the work, since this sh*t was on day one.