The term "istg" is an acronym that stands for "I swear to God." It is often used in informal communication, especially in text messages and online conversations, to emphasize the seriousness or sincerity of a statement. When someone says "istg," they are typically expressing strong feelings about a situation or promise.
The acronym "istg" is derived from the phrase "I swear to God," which has been used in English for a long time. The use of acronyms and abbreviations in digital communication became popular with the rise of texting and instant messaging, making it easier to convey emotions quickly.