This gets a bit abstract, and in some way feels familiar. I had envisioned this idea as fitting into one of my conlangs, but I don't really see it as part of any one of them right now.
Since I formulated it with a rather clear idea of whether to use pre- or suffixes as well as pre- or postpositions,, the post will assume prefixes and prepositions. I guess fixing this might make the text significantly easier to read.
Let us imagine a system whereby prepositions are marked as to what kind of a constituent they pertain to. By this, I mean 'whosoever moves or is moved, whosoever is located or has been made to be somewhere'. Now, we get maybe three obvious markers, and we could of course let these be similar to, say, the relevant case morphology or something. Hold on.
When a subject moves somewhere, the preposition expressing this movement could be imagined to have a pronoun standing in front of it, something like
he goes he in the house
Now, we can imagine the pronoun becoming reduced, and also that the person congruence is lost, so it always becomes
I go e into the house
he goes e into the house
Next, we can imagine when an object is placed somewhere or seen somewhere or whatever, that an object pronoun goes somewhere:
Tina saw the man him in the park
Tina saw the man min the park
and as the reduction and loss of congruence happens, we also get
Eric put the shoes mon the shelf
We can imagine one more obvious distinction here without going too fine-detailed, that of oblique objects. Let's use i- for this.
He went eto sea iin winter
The distinction between 'he went eto sea iin winter' and 'he went ein winter' is that in the latter, it is just a statement about what he did, in the former, the point is that it is in winter he in fact went to sea.
Now, finally, let's imagine that some kind of indefinite pronoun (any, one, some?) appears when there's an object or tool implicit in the verb itself. Let's use ni- for this (from 'any').
he painted nion the wrong wall.
he fired niat the thief
Now, I imagine such implicit tools or objects (or obliques) may sometimes get quite culturally quirky, and one possible path one could see is having, for instance, verbs of sex omit a lot of nouns, such that, for instance, penetration would be expressed as
pushing ni-in it,
oral sex as
licking ni-on it,
Here, we can imagine two rather opposite situations:
- omission is something that is naughty, used to quickly get to the point, and so the 'non-naughty' way of talking about these use more, uh, referential nouns. In this case, ni- becomes a bit of a "naughty" morpheme in some contexts.
- omission is something that is used for euphemism, and in this case, ni- becomes a "polite" morpheme for talking of certain things.