The exact origin of the Aramaic forms cannot be ascertained. The underlying prototype *parpaḫīn- is not compatible with Sumerian {babbar.ḫi} and early Akkadian papparḫû ‘purslane’, but comes very close to the later Akkadian forms (EDA I 392).
According to Zimmern 1920, 434, the widespread meaning “to understand; to give a clear decision, to explain” for *p-r-š in Aramaic (and Hebrew) may be due to the influence of Akk. parāsu.