What does "...proverbs are the palm-oil with which words are eaten" mean in Chapter 1 of Things Fall Apart?

There is a saying in Igbo land that "when a proverb is used and explained to a man, that his mother's bride price was paid in vain." The mark of an elder in Igbo land is the ability to use proverbs dexterously in social conversations. A man who is not seasoned in the use of proverbs is seen as immature or foolish in talk. Proverbs are particularly useful because they are used to state the length and breadth of a matter in such a way that children and women are kept outside the loop, thus elders are able to freely converse in the presence of children and women without fear of letting too much out.

Palmoil is a very important staple used for cooking or even on its own for many purposes in the dietary life of the Igbo man. It is so important that there is hardly any food that palmoil does not feature as a part of the meal. Thus the use of the metaphor of proverbs, the oil with which elders eat words. The metaphor shows how important proverbs are in Igbo social discourse when we come to understand the important role of palmoil in the cooking and dietary culture.