Unfamiliar Apple ID keep popping up for password

Recently I’ve tried to update some apps in my iPad. A pop-up with title ‘Sign In to iTune Store’ requiring me to enter the password for an Apple ID (that isn’t my existing...it’s a google email acc which I found unregistered with google.com). The pop-up only allow to enter password but not to change the Apple ID shown. I keyed in a few guesses but are all incorrect and eventually it was blocked. I couldn’t find in my settings or anywhere in my device that link me to this Apple ID.

I highly appreciate if someone would help.