In folk tradition the walnut tree stands for wisdom and hidden knowledge, its nut shaped like a brain inside a hard shell. Dream books read it as effort needed to reach what is valuable.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.