Explain simply why a centuries - old Scottish proverb is the correct answer to: Passage: The idiom is apparently derived from a centuries-old Scottish proverb, though some other references to pigs flying or pigs with wings are more famous. At least one appears in the works of Lewis Carroll:

Question: Based on this passage, where did the phrase when pigs fly come from?. Explanation:
The important part for answering this question is: The idiom is apparently derived from a centuries-old Scottish proverb, though some other references to pigs flying or pigs with wings are more famous.