Whoever ate all the desserts on the table, will get their just deserts when the stomachache hits.
Just Deserts [THINK: not the sand; deserved]
Just Desserts [THINK: just sweet food (double letters)]
“The particular sense of desert that appears in just deserts ultimately derives from the Old French verb deservir meaning “to deserve,” and has been around in English since the late 1200s. Dictionary.com defines desert as “reward or punishment that is deserved.” The idiom get/receive one’s just deserts means “to be punished or rewarded in a manner appropriate to one’s actions or behavior.”
“…Dessert with the double s ultimately derives from the French desservir meaning “to clear the table.” Dictionary.com defines dessert as “cake, pie, fruit, pudding, ice cream, etc., served as the final course of meal.” While it is certainly true that a meal of cake, and cake alone, could be called “just desserts,” this is not the spelling or meaning of the phrase that has been around in English since the late 1300s.”
[read more about it on blog.dictionary.com]