Final answer:
Whalers originally killed whales for their oil, which was used in making various products.
Step-by-step explanation:
Based on the information in the passage, it can be inferred that whalers originally killed whales for their oil. Whales, particularly sperm whales, were hunted for their oil which was used in making candles, ointments, cosmetic creams, and industrial lubricants. One large whale could produce up to 500 gallons of oil, making it a valuable resource.