I only know the (correct) answer to your FIRST question ...

'noob' (spelled incorrectly, it should be NUB) is an acronym used in the Military that refers to any New Personnel assigned to a Unit that are not familiar with the procedures and practices; and required duty performance of their position in the Unit. They are classified as a N.U.B. (Non Useful Body) until they are trained up to the standard they are required to pefrom in their position in the Unit.

This acronym was borrowed from the military and applied to the gaming community to apply to anyone who is new to the game and doesn't know what they are supposed to be doing in the game.

The spelling 'noob' arised because people not familiar with the origin of the term spelled it the way it sounds instead of the acronym that it stands for.

There are many other military terms that are commonly used by people that don't realize the military origin.

Short end of the Stick - (Originally **** end of the stick) originated from a military prank ... in the old days, when hundreds of soldiers would use the same dug trench latrine, the ***** would pile up and soldiers would have to use a stick to push the pile down before they could sit and defecate. They would then leave the stick by the latrine door for the next soldier to use. As a prank, sometimes a soldier would turn the stick upside down so that when the next soldier reached for it they would get "the **** end of the stick"

Boat load, butt load, **** load - (Originally Ass Load) originated from soldiers overloading their Mules (Asses). In the old days (before motor vehicles) the Military used Mules (Asses) to move their equipment and soldiers would load their Asses to the point of collapse, then remove a small amount until the Ass was able to carry it leading to the term "now that's an Ass load". This term has had variants applied by people not familiar with the origin, or to be more child friendly.