Can humidity ever hit 100%?
Yes, humidity can hit 100%. Relative humidity is the measure of the amount of water vapor in the air relative to the maximum amount of water vapor the air can hold at a given temperature. When the relative humidity reaches 100%, the air is holding the maximum amount of water vapor it can at that temperature, which means the air is saturated. This is also known as the dew point, as it is the temperature at which dew begins to form or condensation occurs. It is important to note that 100% humidity doesn't mean the air is holding all the water it could ever hold, but rather that it's holding all the water it can at that specific temperature.
so why 100% humidity is called 100% if its not water?
Let me see if I can understand your question correctly and give you my interpretation. 
100% humidity refers to the maximum amount of water vapor the air can hold at a given temperature.  100% water may means the substance consists of water only but nothing else, which is not in the case for humidity and a different concept.