Where did "Sweet summer child" originate?

For when someone is being naive. Was it Game of Thrones? Or did GRRM get it from some older saying?

I suspect it was GRRM. After all, it does arise from a circumstance where summers last for years and even decades, before moving into a winter of similarly excessive length. Not a common real world scenario.

But that’s just my WAG on the question. Perhaps there were other tales told of locations with endless summer and hence people who thought the world was designed for their comfort and pleasure.

Always thought of it as a “Summer of Love” thing. Flower children. Spark a joint to celebrate the fiftieth anniversary!

*See that girl barefootin’ along
Whistlin’ and singin,’ she’s a carryin’ on
There’s laughin’ in her eyes, and dancin’ in her feet
She’s a neon light diamond, she can live on the street.

Take a vacation, fall out for a while
Summer’s comin’ in and it’s goin’ out in style
Lie down smokin,’ honey, have yourself a ball
'Cause your mother’s down in Memphis, won’t be back till the fall.*

– “The Golden Road (to Unlimited Devotion),” The Grateful Dead, 1967

Yup. I read most of the books until they got too bloated. And watched the show until I burned out on certain aspects…

Summer Children were those born during “Summer” on that unnamed world. Seasons lasted for years–sometimes many years. So they were not prepared for the Winter that would eventually come And perhaps last for many years…