From ChatGPT:

The origin of “sod” as a slang term comes from British English, where it has been used since the 19th century. It is derived from “sodomy,” which refers to non-procreative sexual acts, and has historically been used in legal contexts with negative connotations. Over time, “sod” became a more generalized term of abuse or insult, detached from its original specific meaning related to sexual acts.

In the context of “sod off,” the term “sod” is used as a derogatory noun, but it has become somewhat less offensive over time, often considered more cheeky or informal rather than a serious insult. The usage of “sod” has expanded beyond “sod off” to include expressions like “poor sod” (a term of sympathy for someone in an unfortunate situation) and “lucky sod” (someone who is particularly fortunate), showcasing its versatility in British slang.