Derived from the cliché "digging yourself into a hole" (In a conversation; where someone keeps saying things which make their own situation more and more awkward). "Drop the shovel" may be said to the person digging themselves into the hole by another member of the conversation concerned for the person's welfare, indicating that they should stop talking to avoid making the situation any worse. Created by the only Matthew Jones in Cardiff.
Jake: And I said to my girl, "Shut it, fatty!" Ha. But she got the joke.
Tom: Ha! It's funny because she is a little bit chubby!
Jake: No...that's not why it's funny. My girl's not chubby.
Tom: Nah but she's got a bit more cellulite than most.
Tom: Ok, it's not just cellulite I know. She must have an eating disorder righ-
Matt: DUDE. Drop the shovel.