The rule that adding an -er to a word you get the agent. https://en.wiktionary.org/wiki/-er#Etymology_1 https://en.wiktionary.org/wiki/-er#Etymology_1 https:/

The rule that adding an -er to a word you get the agent. https://en.wiktionary.org/wiki/-er#Etymology_1 https://en.wiktionary.org/wiki/-er#Etymology_1 https://en.wikipedia.org/wiki/Agent_noun https://en.wikipedia.org/wiki/Agent_noun