If you’re not familiar with F & E, then you probably aren’t going to be able to help here. Move along, is my advice.
But if you’ve read it, you know that it describes the journey of Golan Trevize and Janov Pelorat, trying to find the original home of all humanity–Earth. Along the way they stop at Solaria, and take aboard the hermaphroditic Fallom. Not long after, they reach Alpha Centauri, and attend a concert played on ancient instruments…actually a string quartet. At some point, Fallom sees something, and says,
It’s a feeful! It’s a feeful!.
And she (for it was agreed to use the feminine) gets shushed down as if she’s said something bad.
So my question is, what was a “feeful” and why was it bad for Fallom to mention it?