TTBOMK

TTBOMK stands for "to the best of my knowledge." It is very similar to the much more commonly used acronym AFAIK.

Those who precede a statement with TTBOMK want to convey a degree of uncertainty in what they're about to tell you. For example, a friend who does not trust their memory of their college Physics classes might tell you that "TTBOMK, the Sun is located ~92 million miles from Earth." (In this case, however, your friend's memory can be trusted.)