Well the origins were laudable, it’s just that it was shortly thereafter extended for racist means. Binet and Simon wanted to see if they could devise a test to measure intelligence in children, and they ultimately came up with a way to measure a child’s mental age.
At the time, problem children who did poorly in school were assumed to be sick and sent to an asylum. They proposed that some children were just slow, but they could still be successful if they got more help. Their test was meant to identify the slow children so that they could allocate the proper resources to them.
Later, their ideas were extended beyond the education system to try to prove racial hierarchies, and that’s where much of the controversy comes from. The other part is that the tests were meant to identify children that would struggle in school. They weren’t meant to identify geniuses or to understand people’s intelligence level outside of the classroom.
From the wiki, the idea comes from an essay that somebody has written about a conversation they had with a friend about the struggles of chronic illness. The conversation took place at a restaurant, and she grabbed the spoons for use in a metaphor because there were spoons nearby. She gave her friend a set of spoons, and every time her friend mentioned doing a task, she took a spoon away.
It could have been anything, but spoons happened to be at hand and she wanted to make a physical representation of an abstract concept. The essay resonated with people, so spoons became entrenched. And now I hear people say that they’re all out of spoons to express the idea that they’ve done all that they can that day.