A heiti is a synonym used in place of the usual word for something. For example, jór ‘steed’ might be used in place of the normal hestr ‘horse’. Such words were an essential part of the poet’s vocabulary, where the dictates of alliteration required synonyms that began with the required letter.
Heiti could be derived in several different ways. Some, like the example of jór were archaic word, but synecdoche (a figure of speech in which a term for a part of something refers to the whole of something) and metonymy (a figure of speech in which a thing or concept is called not by its own name but rather by a metonym, the name of something associated in meaning with that thing or concept) were often used. Occasionally, even loanwords were employed e.g. sinjór ‘lord’ from the Latin senior.
Modern scholars view heiti as distinct from kennings, in as much as heiti are single words, whereas a kenning is a circumlocution in the form of a phrase or compound word. Thus, barð ‘ship’ is a heiti formed by synecdoche (barð means part of the prow of a ship, but is used to refer to the ship as a whole), whereas gjálfr-marr ‘sea-steed’ is a kenning for a ship.
The earlier usage of heiti, however, was somewhat broader. Snorri Sturluson, writing in the 13th century, used ókend heiti ‘unqualified terms’ for what we call heiti and kend heiti ‘qualified terms’ for kennings.
There are 155 known heiti for Odin. You can view the list here…
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