Final answer:
A kenning is a compound phrase used in Old English literature to replace a simple noun with a more descriptive expression, such as 'ring-giver' for a king or 'whale-path' for the sea.
Step-by-step explanation:
The term commonly used in Old English literature to refer to the substitution of a compound phrase for the usual name of a person or thing is known as kenning. Kennings are metaphorical expressions that replace a simple noun with a more descriptive phrase, such as “ring-giver” for king, and “whale-path” for sea.
This figurative language was prevalent in Old English poetry, especially in works like “Beowulf”. Unlike metonymy, which uses a related attribute or concept to stand in for the thing itself, and synecdoche, where a part is used to represent the whole or vice versa, a kenning creates a compound phrase that is often vivid and imaginative, making it a unique feature of Old English diction.