What is the origin of the term "no shilly-shallying, no dilly-dallying"; and what is the difference between 'shilly-shallying' and 'dilly-dallying'?

https://www.etymonline.com/word/shilly-shally#:~:text=shilly%2Dshally%20(v.),%2Ddally%2C%20etc.).

Shilly-Shally means "to vacillate, hesitate, act in an irresolute manner," dates back to 1782, from the adverbial expression to "stand shilly-shally" from 1703), which in turn came from "shill I, shall I" (1700), a fanciful reduplication of shall I? (similar in meaning to "wishy-washy", or "dilly-dally".

In 1782 the verb dilly-dally came to mean something similar: "loiter, delay, trifle," also dillydally, This was probably a modification of the reduplication of "dally" from 1841.