Ask A Korean has a great post on the reason why a disgruntled fan might want to lob a few toffees at the returning Korean football team. He has a few explanations why “Eat Yeot” is considered an insult.
The article promted an LKL reader to add a different story about eating yeot as a figure of speech:
In this instance, yeot (엿) is used as swearing or in a vulgar/crude way. In my school days, yeot was used in good ways. Just shows how language is being evolved by the users and the changes in a society.
Yeot was a valuable and rare treat for hungry children then.
Parents used 엿 and tteok (떡) wishing their children’s success during the time of the entrance exams for schools and universities. Their stickyness is metaphoric to ‘not failing/falling out’ of their aim/target.
Also there is an expression, 장의입고 엿 먹는다. (Jangeui ipgo yeot mongnunda: Under a jangeui, one eats yeot). Jangeui is a long cloth which used to cover a lady’s hair and face when on an outing. So the explanation of the expression is that Under formal/proper attire, one behaves casually/unlady-like by eating yeot/snacks.