I'm one of those boomerang employees. It was the best thing I ever did. Left on good terms, learned a ton of new stuff at a few other companies, and ultimately came back a much improved employee, despite being a high performing worker to begin with.
Didn't realize there was a name/term for it, but it makes a lot of sense.
Where I'm currently working, a coworker left a couple weeks ago. He really wanted to stay, he LOVED the company, but his position wasn't a great fit for him and he found something else.
He told me that when he told HR "I hope I will come back some day", HR replied: "until I'm head of HR, no one that leaves will ever be considered again".
When I left my last job (BigTechCo) I was explicitly told by HR and my manager that I'd always be welcome back, just reach out. That company got a lot wrong but the HR department and my immediate management chain really did a great job.
Didn't realize there was a name/term for it, but it makes a lot of sense.