The process by which we get wheat—known as threshing—produces a leftover that is thrown out. This leftover is known as chaff. More generally, chaff refers to anything that is worthless.
Colloquially this word is used to describe what happens when skin wear away due to constant rubbing (think of running sockless in a pair of ill-fitting shoes.) To chafe can mean either to irritate or be irritated. (e.g.- He chafed at the constant squawking of birds vs. the birds chafed him with their constant squawking.
1. Because Johnson’s biography is filled with so many cherished insights, any criticism asserting that the work is mostly chaff is —-.
2. CHAFE (Find the antonym!)