A Hidden Green Man

This mysterious face peeks out from the underside of a font inside the Church of the Holy Rood in Daglingworth, Gloucestershire. He appears to be a "Green Man", but rather than spewing foliage from his mouth as is common with the earlier examples, this fellow is more of a "foliate head", his visage nestling among leaves.

The font was sculpted during the 1400s and is quite plain, it has no other carved features. The Green Man is concealed, you have to crouch or kneel down then look upwards at its underside.

Why was he hidden, and what does his image mean here?