“Show your true colors” began with real flags in naval warfare. Today it means revealing your real character, often in a telling moment.

“Which” can appear in restrictive clauses, especially after a preposition. “That” is often preferred, but “which” is not incorrect.

Credible means believable or trustworthy. Credulous describes someone who believes too easily, often without enough doubt.

Solecism is named after Soli, a city linked with mixed or faulty Greek, and the word later came to mean a grammatical error.