The Japanese language has a special group of words which repeat mostly two syllable word like pera pera, para para, don don, suku suku, that are used adverbially for examples;
Pera pera eigowo hanasu– speak English fluently.
Iki Iki shiteiru – look vivid (fresh)
Don don iku – go fast
Para para furu – rain drizzlingly
Muka muka suru – feel sick (angry)
Pera pera mekuru – turn the page at random
Zuki zuki itamu – ache acutely
Suka suka tooru - pass smoothly
They look like onomatopoeias, but they are not. They don’t reflect any sound, and they are all used adverbially, not as interjections.
I don’t know whether such usage is special to Japanese language or not. Are there a lot of similar form of refrains of nonsensical (on their own) two - (sometimes one) syllable words in separation (unlike the type of crisscross, dillydally, riffraff which are single word) used exclusively adverbially except onomatopoeia (which is not my concern) in English and other languages. If there is, I'm curious to know how we call such a group of words or usages.