surprise (one) by (doing) (something)
To shock, amaze, or astonish one by doing, possessing, or demonstrating something. I must say, he surprised me by his honesty. I thought for sure he'd try to deny it or weasel his way out of a punishment. The kids surprised me by making me breakfast in bed for my birthday.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.