* mel - meaning "honey"
* fluo - meaning "to flow"
Therefore, "mellifluous" literally means "flowing like honey". This is a perfect description for the word's meaning, as it refers to a sound that is sweet, smooth, and pleasing to the ear, just like honey is sweet and pleasing to the taste.
The word entered English in the 16th century, likely borrowed from the Latin "mellifluus". Its use has remained consistent, referring to anything that has a pleasingly smooth and sweet sound.