If Anna is the lead unit in a battle in which she kills the enemy, she has a chance of obtaining Gold based on her Luck stat as the activation percentage. Anna may also obtain the skill Profiteer through the Merchant class. This, along with her high base luck and excellent luck growth, make her fittingly the best unit for making money.
Ikkaku Senkin is a Japanese phrase that roughly means "one grab, a thousand gold", meaning obtaining money through little effort. It is also one of Anna's Japanese cut-in quotes in both Awakening and Fates.
Make a Killing is an english idiom used to describe making a lot of money very easily. It is also a pun on the fact that Anna needs to kill an enemy for the skill to activate.