The antonyms for the word "fittingness" could be unsuitability, inappropriateness, impropriety, unfitness, or incongruence. These words refer to the state of not being suitable or appropriate for a particular purpose or situation. They indicate the absence of a proper fit or match between two or more things, causing them to be out of place or out of sync. For example, a dress that is too large or small for someone would be considered unfitting, while a joke that is deemed inappropriate for a particular audience would be considered improper. The antonyms of fittingness suggest a state of discomfort, mismatch, or disorder.