Particles such as “min,” “fī,” “ilā,” and the lām of purpose express relations requiring connected terms. The relation denoted by “fī,” for instance, is intelligible in context by identifying what is in what.
Metaphor in a particle is not explained merely by substituting one independent noun for another. The issue is how one kind of relational meaning is likened to another.
Terms such as beginning, containment, and end-point can name relational meanings for analysis, but those names should not erase the particle's dependence on its grammatical attachments.