Vault Stitch is also known as Fan Vaulting and Church Roof Stitch. No Swedish name has been found. Let me know if you have any other names for this stitch.
Mattia suggests, Point de Voûte.
I discovered it in Mary Thomas's Dictionary of Embroidery Stitches, where it is worked in the order of the purple stitch:
This way a LOT of thread is needed.
With yellow thread I changed the stitching to save thread.
Compare the back:
Once you have got the rhythm, you will get 'hooked' and work the stitches fast.
This is what it looks on my Aida sampler:
Fill this square with orange and yellow Vault Stitch.