In Old English poetry the kernel form of riddlic metaphor
is the kenning,
a Nordic device for calling something by a name it is not,

then modifying it with a contextual clue.44

Examples of kennings include:
bone-house (body) battle-light (sword) G's candle (sun) sea-horse (ship) whale's road (sea) battle-snake (arrow)
In each case the tenor is hidden in riddlelike fashion
and the vehicle appears as the second element of the compound,
the gap (presenting a paradox and giving a contextual clue) as the first element.

The two terms of the kenning make up part of the analogy inherent in metaphor according to Aristotle,45 so that, for example:
body/bone X house/strut
sword/battle X light/hall
In each case the analogy may generate four separate kennings, each a miniature metaphoric riddle. The kennings are:
1. bone-house (body)
2. body-strut (bone)
3. strutted body (house)
4. house-bone (strut)
1 . battle-light (sword)
2. sword-hall (battle)
3. hall-sword (light)
4. light-battle (hall)
Each of the kennings could be spun out into a riddle. For example, we might take bone as our solution, and using the metaphor of the body-strut begin:
I am the strut and strength of body,
The unnailed timber of a living house.
I hold flesh, shield lungs, stiffen arms;
I am brain-hoard and hand-shape,
Unknown to the talking and rising tongues.
The riddle spins out the principle of the kenning. Call the creature something it is not. Modify the calling by a catch of contextual truth producing paradox. Metaphorically the bone is a strut, paradoxically a body-strut; metaphorically a timber, paradoxically unnailed. The list of attributes reinforces the real bodily context, but the creature claims to be curiously absent from two tongues (the second of which is the seed of another riddle). By solving the riddle we raise to consciousness not only the bone but the set of kennings implicit in the central metaphor. We discover not only body-strut but house-bone.