Taken literally, "einfallen" means "to fall into". But the meaning that makes it one of the most useful German verbs is a little more abstract ;)
einfallen, der Einfall, einfallsreich, reinfallen
A thorough look at the meaning of "los", its various useful prefix verbs and the noun "das Los", and what a raffle token has to do with fate and parking lots.
los, lose, das Los, los sein, loslassen, losgehen,
The core idea of this root was:
It doesn’t have any other relatives besides to fall and fallen (and “to fell” and “fällen”) in German and English and it is notably absent from the Latin branch of the Indo-European family. There, the word for falling was *kadere, which is the origin of words like cadence, incident or case.