Unlikely
No, 'likely' is not a prefix.
Gy
The prefix "circum" typically means around or surrounding.
improbable
greece most likely not sure
It means "not" as in "not likely."
pro
One likely possibility would be "epi."
The prefix "DIS" in disavow most likely means:
Prefix=IN
The prefix for inadequate is in-. The prefix in- means not.
The prefix for include is in-. This prefix means not.