If you use the English word “darky”, you are very politically incorrect. It’s an old term for black people which is considered rude and offensive. If, however, you give “dárky” here, you are a generous “stědrý” person on “štědrý den”, or generous day. “Dárek” is the singular form of the word, gift. “Dárky” is plural. Even in the dark days of winter, it’s good to give than receive lots of dárky.