A kenning is a type of compound metaphor which is very commonly found in Anglo-Saxon and Old Norse poetry and prose. The etymology of the word itself gives us some indication of how these conventional phrases were used: "kenning" comes from the Old Norse "kenna," which meant "to know." This word survives in the modern English phrase "beyond our ken," meaning beyond our understanding, and is cognate with words like "cunning" and "canny." The point is, a kenning was something the reader was expected to know and recognize, even though it doesn't describe something directly. Most kennings would have been used so often that readers would associate them immediately with what they represented.

Examples in Beowulf include the very famous "whale-road" in line ten, "hronráde" in Anglo-Saxon. This means the sea, as in a road traversed by whales.

Another great example, used several times, is "béaga bryttan" or "giver of rings." This means a lord and helps us to understand the ceremonial relationship between lord and vassal in Anglo-Saxon culture, which was solemnized by the giving of a ring. This was supposed to represent the lord's acceptance of his duty to provide fiscally for the vassal.

Later, we see an interesting kenning, "beorht béacen godes," used to describe the sun. This literally means "bright beacon of God" and is interesting because it contributes to the debate around the Christianity of Beowulf and whether the Christian elements were added later. This kenning indicates that the Anglo-Saxon language, at least, continued to accumulate new kennings long after Christianization.

Kennings are metaphorical compound words, and they were used to great extent in Old English and Old Norse poetry. They function as a way to make an ordinary noun more descriptive or awe inspiring. For example, "teacher" sounds mundane. "Student-transformer" sounds way better. Beowulf has plenty of kennings. One of my favorites is "sleep of the sword" instead of "death." "Breaker of rings" refers to a king and the action of breaking gold rings off of his arm to give to someone else as a reward. Another one that I especially like is "mind's worth" for "honor." Most readers know what honor is, but "mind's worth" seems much more immediately descriptive and accessible in terms of conveying meaning. "Whale road" and "sail road" are both used to describe the sea.

Instead of giving us an abstract word to stand for an object, a kenning describes the object by comparing it to something else, usually mashing two concrete images together to paint a vivid picture in the reader's mind.

Beowulf makes frequent use of kennings, which add life and zest to this epic poem. Some examples are as follows:

A monster like Grendel, who comes and kills at night, is called, quite aptly, a "twilight-spoiler." He does, in fact, ruin the merry times at night in the mead hall.

The text refers to a sword as "filed leavings." This makes sense when thinking of how metal is sharpened and shaped into a sword: it is what is left (the "leavings") when all the unnecessary metal is honed away.

A battle is called a "sword storm," and that too paints a vivid picture of what a medieval battle must have been like, with swords flashing like lightning and crashing like thunder.

In Old English, a "kenning" is a compound expression that has a figurative or metaphorical meaning. An example is "light-of-battle," used to mean a "sword" in the following example from Beowulf: "But the warrior found the light-of-battle was loath to bite, to harm the heart." Another example is "battle-gear," meaning "armor," and "battle-sweat," to mean "blood," as in the following example, "That war-sword then all burned, bright blade, when the blood gushed o'er it, battle-sweat hot." When Beowulf is battling Grendel's Mother, he refers to losing "battle-sweat." Kennings were common in Anglo-Saxon and Viking literature and were used to add poetic dimension to terms that were often used in their language, such as the sea, battles, or armor. Kennings use metaphorical language to describe these common objects in new and descriptive ways. 

It should be noted in this regard different kennings have been used to describe a single object in different parts of Beowulf. For example ‘sea’ has been described as “sail road” and “swan road” in different sections of this Anglo-Saxon poem. Other good examples of kenning include: “the foamy-necked floater” (used for ‘ship’) and “sea wolf of the depths” (used for ‘Grendel’s mother’).

A kenning is a metaphorical phrase or compound word used to name a person, place or thing indirectly. Used primarily in Anglo-Saxon poetry, the epic poem Beowulf is full of kennings. For example, the term whale-road is used for the sea and "shepherd of evil" is used for Grendel. Other well known kennings include "battle sweat" for blood; "raven harvest" for corpse; and "sleep of the sword" for death.