OK, I got one. It was a SS lesson (adult class), not a sermon. And it wasn't the main point of it, just something the teacher mentioned, related (I guess) to the lesson. He said the Bible says "call no man father", so when he was a kid, they never called their father "father". They called him "dad" instead.
I kid you not.
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Hebrews 13:23 Know ye that our brother Timothy is set at liberty