What it means
An exact double of someone, usually a parent, so alike it is almost uncanny. The phrase was likely worn down from the spit and image, the idea that the child is as alike as if spat straight out of the other. Look at the photo and you cannot tell which generation is which.
Usage examples
"Their youngest is the spitting image of his grandfather, same nose, same ears and the same mischievous grin."
"That little boy is the spitting image of his grandfather."
"With the wig on she was the spitting image of the singer."
"She's the spitting image of her mum, right down to that cheeky little side-eye."
"I saw an old photo of his dad at uni and swear down, he's the spitting image of him."
Where it comes from
The phrase is old and a bit messy round the edges. Early forms include spit and image and spitten image, both used for a person who looked uncannily like someone else. Over time that got polished into spitting image. The exact path is debated, but those older forms are well attested in English.
