The phrase combines a thank you for a diamond, a common name for virtual gifts and in-game rewards, with weeb, slang for an enthusiastic fan of Japanese anime and manga culture. As a standalone soundboard clip it has no widely documented single source, so its life online comes from reuse rather than a famous scene. Short thank you clips like this circulate among streamers, anime editors and meme pages, where they are dropped in as instant gratitude with a self-aware, fandom-friendly twist that regular viewers immediately understand.