the word 'sundae' is a 19th-century american english creation, first recorded in the 1890s. its origin is debated but is widely believed to be an alteration of 'sunday', perhaps because the dish was originally sold or consumed as a special treat on that day, or due to legal restrictions on selling soda on sundays which led to the substitution of syrup for soda water in 'ice cream sodas'. another theory suggests it was named after the 'sunday' patent medicine, which contained ice cream and syrup. the spelling was changed to 'sundae' to distinguish it from the day of the week, solidifying its identity as a distinct culinary term.

this word is a loanword and does not have segmentable morphemes based on its current english spelling. it is treated as a simplex form.