As an idiom, "there’s no telling" signifies that a situation is impossible to predict or determine . It is often used to emphasize a wide range of potential outcomes, ranging from the mundane (like what a person might say) to the life-altering (like the recovery time for a medical condition).

Revisiting Larry Fessenden's 'No Telling' - Certified Forgotten

The title refers to the literal secrets kept between the couple and the metaphorical "not telling" of the horrors occurring in the name of progress. It highlights the deterioration of their relationship through secrecy and a lack of transparency.

While not a mainstream hit, it is considered the first in a "thematic trilogy" by Fessenden (followed by Habit and Wendigo ) aimed at reinventing horror clichés. "No Tellin'" in Music