1926 Bungalow window questions

Hi, this post is a leading somewhere and it’s a direction that I need some help in.
I have a 1926 sandstone from bungalow in Adelaide and I am replacing the window in the bathroom.
The window is in the wet area and the shower sprays water all over the sill.
The old timber window frame was rotton so I removed the window.

Can anyone please tell me the name for the timber ‘frame’ that is put in place in the double brick during the construction stage?

The frame is obviously bricked around and concrete lintels are poured on top of the frame…

Try
Window frame and sash
Tho, Installing the window flashing correctly may be a problem