Do you mean these horizontal figures? I canāt find an English translation. They where used to decorate the outlet of the rain gutter. But the rain gutter is somewhere else.
The Dutch word is waterspuger. It contains water and the verb to spit. It spits the water preventing it coming down via the wall. Later rain pipes where used. Also on the picture.
A picture from a ,modern, churh in Lille,France. You can see the whole in its mouth.
I think this is a fairly standard practice among stonemasons. The guy who redid the heads in front of the Sheldonian theatre in Oxford (itās where degree ceremonies are held) modelled them on the then heads (there is no standard title: Rector for my college, Warden for All Souls, Master for thersā) of Oxford colleges. Donāt know who was more offended: the chaps whose heads were displayed or those passed over.