Meaning and local context
In Texas, “over yonder” means At some place over there, usually visible or understood. A Southern directional phrase common in informal Texas speech.
Example in context
A local example is “The tools are over yonder by the shed.” In plain English, that means “The tools are over there by the shed.”
The tools are over yonder by the shed.
The tools are over there by the shed.
How to interpret it
The surrounding sentence is important when interpreting “over yonder”. Use the regional sense above when the situation matches the example instead of relying on the word or phrase in isolation.
Tone and caution
The distance is contextual rather than exact. Because this is informal regional language, tone and situation should guide whether you use “over yonder” yourself or simply recognise it when someone else uses it.