secretreminder
nounUK /ˈsiː.krət rɪˈmaɪn.dər/
US /ˈsiː.krət rɪˈmaɪn.dɚ/
A secret reminder is a hidden note that helps you remember something.
She left a secret reminder under his pillow so he would not forget her birthday.
OTHER MEANINGS
2. A private alert on a phone or device that only the owner can see.
He set a secret reminder on his phone to buy flowers.
3. A coded message used to jog someone's memory without others understanding it.
The spy used a secret reminder in the newspaper to signal the meeting.
4. A discreet nudge between friends about something personal.
She gave him a secret reminder with a quick wink across the room.