‘Even in a little church not five miles from where I am sitting there is a thirteenth century font with a panel on which is sculptured in low relief the diabolical boar trying to uproot the True Vine with his snout.” – Introduction ‘Sir Gawain and the Green Knight’.
The ‘Sign of Jonah’ is at least as old as the Babylonian Fish-Gods as also is the backward looking beast overcome by Marduk amongst others if memory serves.
The hero usually does both…sometimes cutting a way out!
A lot of the composite beasts were originally calendrical symbols anyway with each different section of the bodily form representing a span of time or season.
The Zodiac is an extension of this idea with the figures conceived as alternately swallowing/regurgitating the preceding/following sign…
…In an Endless Round…
The notion of swallowing whole is crucial here and that is not quite the same as devouring perhaps.
The sun can be conceived as swallowed whole each evening…
…The moon perhaps could more readily be regarded as devoured and spat back out over the course of a month.
The sun on its return is always the same sun (re-born) but the moon is new (born).
Both the Sun and Moon are regarded as God-Heads or Gods-Head.
The sections in the original poem of Gawain… were known as ‘Fits’…