fall off a lorry

fall off (the back of) a lorry

(of goods) be acquired in illegal or unspecified circumstances.
The traditional bogus excuse given to the police by someone caught in possession of stolen goods was that the items in question had ‘fallen off the back of a lorry’.
1991 Time Out People buy so much stolen stuff that…you can…buy a video in Dixons and take it round the corner to a pub, say it fell off the back of a lorry and get 50 quid more than it cost you.
See also: fall, lorry, off