Hot-swap in tech means replacing a hardware component without shutting the system down. "Hot-swap the disk" = change the drive while the computer is still running. Workplace tech term. Not concerning. If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in. Most slang of this kind moves through TikTok and group chats, so seeing it in your child's vocabulary just means they are plugged into normal teen internet culture.