"the stuff between bricks is mortar.

LynnT
stacker of drystone walls"

It is indeed, according to the dictionary, 'mortar', but in the Backwoods where I live, the brickies call it 'Gobbo'. The plasterers also call plaster-mix 'Gobbo'. It's the quaint local patois, tha knaws. 👍😄

Backwoodsman,
Friend, acquaintance and employer of a number of brickies and plasterers during his almost 50 years of home-ownership.