This is likely due to the shape of early tassels, which resembled small cubes or dice. The word evolved into "tassel" through Middle English.
Interestingly, the origin of the word "taxillus" is uncertain, but it may be related to the Latin word "tabula," meaning "board" or "tablet."
So, the word "tassel" has a long and interesting history, tracing back to the shape of early tassels and their resemblance to small cubes or dice.