Words have a habit of slowly and subtly shifting in meaning over time, so that after a few centuries they can come to mean something quite different from what they used to. Case in point, today's word.
When you and I think of waiting, our mental image is probably of someone hanging about passively and possibly a little bored. In the 1200s, that wasn't what waiting was about at all - a wait was a watch, guard or sentry, and failure to remain alert could have dire consequences (see Game of Thrones, any episode will do). An alternative sense at the time was to lurk with hostile intent, a sense we retain to this day in the phrase lie in wait.
It wasn't until the 1400s that the meaning to remain in one place began to assert itself. The first waiting room was recorded in the 1680s (presumably that's when the first 10-year-old Cleo magazines and Reader's Digests became available), and the sense of to wait something out (think Australians and their desire to win the Bledisloe Cup) arose in the mid-1800s.
As for that hard-working, underappreciated soul who caters to your every whim at your favourite restaurant before you walk away leaving a pathetic tip, you miserable sod, waiters - or "attendants at the table" - are a creation of the 1560s. Lucky for you they're not waits in the ancient sense of the word. Otherwise you might end up, Game of Thrones style, with a spear in your rear.