What it means
A cheeky way to say keep this quiet or don’t repeat it. You tack it on before a bit of gossip or a confession, as if the nearest lamppost is sworn to secrecy too. It’s pretty old-fashioned and often said tongue-in-cheek, like the classic between you, me and the gatepost, but it still gets a laugh.
Usage examples
"Between you, me and the lamppost, I scoffed the last custard cream and blamed the dog. If Nan clocks it, I’m in deep trouble."
"Between you, me and the lamppost, I reckon they're moving away, but don't you dare say I told you."
"She got the promotion, but between you, me and the lamppost, half the team is already looking elsewhere."
"Between you, me and the lamppost, Darren’s big startup is just him in the shed with a laptop and a panic on."
"Between you, me and the lamppost, I said I was stuck in traffic, but I’d actually slept through three alarms."
Where it comes from
It comes from the older British set phrase between you, me and the gatepost, a joking way to ask for secrecy by dragging in a daft inanimate witness. Lamppost is just a later comic swap on that same template, used for the same wink-wink hush-hush effect rather than as the original form.
