As in "Hickory Dickory Dock; the Mouse ran up the Clock..." (Perhaps there is a separate term for a real word used nonsensically (Hickory and Dock). Is there a word for this sort of usage?)
I have a few ideas that I think fit better than neologism:
- nonce word: "a word used only 'for the nonce'—to meet a need that is not expected to recur"
- logatome: "an artificial word of one or more syllables which obeys all the phonotactic rules of a language but has no meaning"
- pseudoword: "a unit of speech or text that appears to be an actual word in a certain language (at least superficially), while in fact it is not part of the lexicon"
I think the first two are the closest, and the term nonce word has the advantage of being fairly common in literary and linguistic contexts. Logatome might be a little closer to what you're looking for, although it's not quite as specific as your request, I think.
One option is that dickory is a neologism. The main definition of this is:
- a new word, usage, or expression
Wikipedia adds that a neologism:
is a newly coined term, word or phrase, that may be in the process of entering common use, but has not yet been accepted into mainstream language. Neologisms are often directly attributable to a specific person, publication, period, or event.... Neologisms also can be created through abbreviation or acronym, by intentionally rhyming with existing words or simply through playing with sounds.
From the above "dickory" is a neologism, as it was created to rhyme with "hickory".
Some famous examples of neologisms are from Lewis Carroll, who was apparently known as a neologistic poet. His famous poem Jabberwocky begins with the lines:
"Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious *Bandersnatch*!"
The words in bold are neologisms that he created in order to write the poem.
Another option is simply calling dickory a nonsense word:
A nonsense word, unlike a sememe, may have no definition. If it can be pronounced according to a language's phonotactics, it is a logatome. Nonsense words are used in literature for poetic or humorous effect.
Related to this is gibberish:
Gibberish (sometimes spelled Jibberish) is a generic term in English for talking that sounds like speech, but carries no actual meaning. This meaning has also been extended to meaningless text or gobbledygook. The common theme in gibberish statements is a lack of literal sense, which can be described as a presence of nonsense. One of the more famous examples of using gibberish in literature is the poem, Jabberwocky, by Lewis Carrol.
Because "Jabberwocky", Carrol's nonsense poem, is referred to as both neologistic and gibberish, I would think that any of these terms could apply.
The answer my English teacher would have given is that this is a contrivance. That is, it's a word contrived specifically for the purpose of a rhyme or alliteration. This means the poem could risk being criticised as "contrived".
But I feel like this doesn't fully answer your question since the word contrivance can be used for anything that's contrived, not just words.
I'd also agree with the terms neologism, nonsense and gibberish but neologism can mean a new word for any purpose, nonsense can mean any content that makes no sense, and gibberish tends to refer to spoken word, not written. None of these are specific to poetry or other writing either.