Imagine my surprise to discover “growing pains” are a real phenomenon for some children and not merely a colloquial phrase! A quick google yields many hits on these “real” growing pains. These overwhelm the usage I was looking for: any problems encountered early in an undertaking.
Growing pains probably have little to do with growth. The pains are most common in children ages 4 to 12, whose growth rate is lower than that of both infants and adolescents; most growth occurs near the knees, but the pain isn’t centered there; children who have growing pains grow at the same rate as those without. straightdope.com
breakingmuscle.com says “the origin of the term ‘growing pains’ is disputed. The Cleveland Clinic for Children maintains that the phrase was coined in the 1930s to 1940s, while several other studies claim that the term has been around since the 1800s.”
I guess I was lucky to never encounter these physical growing pains.