出典:Wiktionary
From whack + a + mole (“small, burrowing, insect-eating mammal of the family Talpidae”), from the arcade game Whac-A-Mole which involves quickly and repeatedly hitting the heads of mechanical moles with a mallet as they pop up from holes.[1] The name of the arcade game was coined in 1977 when it was first sold in the United States; the original game released in Japan in 1975 was called モグラ退治 (Mogura Taiji, literally “Mole Extermination”).
whack-a-mole (countable かつ uncountable, 複数形 whack-a-moles)