Also, breaking a word down into its morphemes goes far to establishing a general expectation of the word's meaning. For example, today I was looking at the not very common word "Epeisodos," where we get "Episode." But you can see the meaning is along the lines of "upon course into" and in context "penetration" is precisely the idea -- as Epikouros is talking about the penetration of particles into the mind.
Epíkouros, Peri Phýseōs, Book 25, P.Herc. 1056 col. 12 (fr. B 34)