Do you know ghouls from goblins and ghosts?
Old English cenning "procreation; declaration in court," present participle of ken (v.). From early 14c. in senses "sign, token; teaching, instruction;" c.1400 as "mental cognition." From 1883 as "periphrastic expression in early Germanic poetry;" in this sense it probably is from Old Norse cognate verb kenna "to know, to recognize, to feel or perceive; to call, to name (in a formal poetic metaphor)."
concise compound or figurative phrase replacing a common noun, especially in Old Germanic, Old Norse, and Old English poetry. A kenning is commonly a simple stock compound such as "whale-path" or "swan road" for "sea," "God's beacon" for "sun," or "ring-giver" for "king."