Here's a breakdown of its etymology:
* Old English: "swimman" (to swim)
* Middle English: "swymmen" (to swim)
* Modern English: "swim" (to swim)
The suffix "-ingly" is an adverbial suffix that indicates manner or state. It was added to "swim" to create the adverb "swimmingly," which means "smoothly, easily, or without difficulty."
Therefore, "swimmingly" came about through the combination of the verb "swim" and the adverbial suffix "-ingly," reflecting the image of something moving effortlessly and smoothly through water.
The first recorded use of "swimmingly" in English dates back to the 16th century. It was likely used initially to describe the movement of a boat or ship through the water, but its meaning has since expanded to encompass any activity or situation progressing smoothly and easily.