Welcome, Orchard.

To add a tiny bit to Father Steve's info, I was taught when studying the Colosseum that the base phrase was pollicem vertere meaning “to turn the thumb”. It is not certain that the popular conception that 'thumbs up = spare him' is correct. Neither, come to that, is there a lot of solid ground for the other thing we all 'know' about the games ~ that they all faced the Emperor's box saying "We who are about to die salute you". I learned that there seemed to only be one documented example of this (Suetonius?) and that was from an execution event (one of the naumachia staged by the nice Claudius!) rather than a gladiatorial contest.

Sorry, can't help with the tickly throat thing.