A zirk fitting is what’s used on a grease gun for adding liquid as opposed to a schrader fitting for adding air. The only reason to install a fitting is if they needed to add something periodically or if they had to seal the area and add it after there was no other access.
So they needed to add a viscous grease-like liquid either periodically or after… back fill? …probably to deal with moisture problems.
So you’d inject something that would stop moisture intrusion but which after a while would become ineffective due to… dilution… soil movement…chemical breakdown?
Someone might install a pan to serve as a sight glass… to check moisture levels on the exterior of the wall without allowing seepage to come under the wall and into the living space.
If you ever figure this one out, please post it.