There’s a term / name for this method.

Emotional freedom technique (EFT)?

I had never heard of this..

Seems it is for relieving emotional stress but i had only used it specifically to wake up at a specific time.

https://www.healthline.com/health/eft-tapping

EFT is unrelated to head tapping for setting internal wake up calls.

In EFT you're tapping on the end points of the meridian lines to send a kind of "reset pulse" to clear emotional issues. (At least that's the concept.)

To set a "wake up call" you (basicplus2) tap your head with your finger, but probably not on a meridian point, and you're not trying to clear an emotional issue. Also, some people tap their whole head on their pillow instead.

Ah right, thanks, I wasn’t sure if the two were related.

Cheers!