What it means
It's the classic deal of mutual back-scratching — you do me a solid, I do you one right back. When someone needs a favour and you wanna remind 'em it's a two-way street, this is your go-to. No free lunches here, just good old-fashioned teamwork with a wink.
Usage examples
"Look, I'll cover your shift this weekend, but you scratch my back and I'll scratch yours — I need next Friday off."
"Politics is just you scratch my back and I'll scratch yours dressed up in suits and ties."
"Don't expect a favour without offering something back. Around here it's you scratch my back and I'll scratch yours."
Where it comes from
This one's old as dirt, mate. Goes back to at least the 1600s, with a literal meaning — sailors and navvies would scratch each other's backs where they couldn't reach. By the 1700s it had already become a cheeky metaphor for 'you help me, I'll help you'. Proper working-class wisdom that stuck around.
