"SMH" stands for "shaking my head." It is an acronym often used in digital communication to express disappointment, disbelief, or disapproval about something. When someone says "SMH," they are often indicating that they cannot believe what they are seeing or hearing, or they find a situation frustrating or ridiculous.
The acronym "SMH" likely emerged from the growth of internet slang and texting culture in the early 2000s. It reflects a form of expression commonly used on social media platforms, forums, and messaging apps.