Here's a breakdown of its likely origin:
* Origin in Religious Belief: The phrase likely evolved from a time when people were more deeply connected to the land and relied on its bounty for survival. The land was often seen as a gift from God or a higher power. So, saying "for land's sake" could have been a way of invoking that divine power as a source of exasperation, similar to saying "for God's sake."
* Evolution of Meaning: Over time, the religious context faded, and the phrase became more of a general expression of frustration or amazement. The "land" part continued to represent something vast and impressive, even if it wasn't specifically religious.
It's important to note that there's no definitive historical record of its precise origin. However, the phrase's meaning and its use in expressing surprise or frustration suggest a long history rooted in humanity's connection to the natural world.