Chazal tell us that we should always make sure to speak לשון נקיה, a clean language (· פסחים ג). How does one make the determination of what is included in the category of לשון נקיה?
Well, you start out when you’re a young child and your mother says to you, “Don’t say that!” If your mother tells you that, then you’ve started out on the road towards knowing what is not לשון נקיה. And if your mother wants to wash your mouth out with soap, then you’ve surely received a very important lesson in the sugya of לשון נקיה. That’s number one. שמע בני מוסר אביך ואל תיטוש תורת אמך. It’s a very important lesson, by the way. Your mother, at home, is your first teacher. Your first lessons are at home. And sometimes, your father as well.
And then you begin to learn outside the home as well. In Slabodka, they never said the word שלעכט, the word “bad.” They never said the word שלעכט. Never. I was there six years. Six years – and they never said the word שלעכט. “Not good,” they would say. But they never said שלעכט. They never referred to a goy as a “sheigetz.” Because that’s a שקץ. The word “sheigetz” comes from the word שקץ, a disgusting creature. “Sheigetz” is שקץ. But a goy is not a שקץ. He’s a צלם אלוקים. He’s not the best picture of צלם אלוקים, but he’s actually a צלם אלוקים. So, in Slabodka, they called a gentile an ערל or a גוי – but they never said “sheigetz.” The word “sheigetz” is never found in Slabodka language.
So, in a good environment, if you make sure to stay in a good environment, you’ll pick up what is called לשון נקיה.