By the time we came along, German was only used for conversation we "didn't need to know about", and for teasing or admonishing us.
For instance, if we asked why kids couldn't drive cars, or why we couldn't have only ice cream for every meal, one of them would laugh and say what sounded like "Du bist fer-icht!", meaning "you are crazy" or "you are goofy". Now, the only way I can find out if 'frricht' is an actual word is with Google Translate...and nope, it isn't. So, what's a word for 'crazy' in German? Ahh...verrückt.
'Course, there were some words Google doesn't know, like "schluparsch", meaning a...well, a willfully messy, dirty person. We understood it like "slop ass"...lol Heaven forbid you should be called that!
One of my clients is the age my parents would be now, and she grew up with German at home too. I was applying lotion to her back after her shower and it was a little cold--we were both laughing, and she called me something in German that I hadn't been called in 50 years.
'Course, I didn't write it down, and now neither of us can remember what it was...lol I'll add it here if it comes back to me. But if YOU have a suggestion, add it in a comment, ok?