Occur, v. i. [imp. & p. p. Occurred(); p. pr. & vb. n. Occurring.]
Etymology: [L. occurrere, occursum; ob (see Ob-) + currere to run. See Course.]
1. To meet; to clash. [Obs.] The resistance of the bodies they occur with. Bentley.
2. To go in order to meet; to make reply. [Obs.] I must occur to one specious objection. Bentley.
3. To meet one's eye; to be found or met with; to present itself; to offer; to appear; to happen; to take place; as, I will write if opportunity occurs. In Scripture, though the word heir occur, yet there is no such thing as "heir" in our author's sense. Locke.
4. To meet or come to the mind; to suggest itself; to be presented to the imagination or memory. There doth not occur to me any use of this experiment for profit. Bacon.
Shades of meaning
Fernald has no entry of its own for occur; he lists it under happen.
He lists it without comment; the entries above explain its neighbors.