I looked it up here: http://www.etymonline.com/index.php?term=zero

Apparently derived from ML zephir and arabic sifr" Oddly enough it doesn't seem to be related to Zephyr which has a different etymology.

Of course we use it represents the digit '0' use for positionally weighted numeric systems, regardless of base. The digits in the number system range from zero to the base minus one. So base 10 uses digits 0 through 9, inclusive; base 2, 0 through 1; base 8 zero through 7; base 16, 0 through 9 AND A through F).

As a noun, it can also refer to the solutions of equations.
It's the "cardinality" (size or magnitude) of the set with no elements.

A zero can also mean an unpopular person.

According to wiki, WWII Japanese fighter planes were called zero after 'Navy Type 0 Carrier Fighter'.
http://en.wikipedia.org/wiki/Mitsubishi_A6M_Zero

It's also used as a verb. To zero an instrument means to set the value to zero. In computers it's often a synonym of "reset" when referring to registers (fast, on-chip memories in which computations are performed).

M-W lists the following synonyms: aught, cipher, goose egg, naught (also nought), nil, nothing, o, oh, zilch, zip

I remember my grandparents rarely said zero, instead preferring "aught" or "naught."

With alphanumeric codes on the computer, it's often difficult to distinguish the numeral '0' from the letter 'O'. On the old teletypes, they used the null symbol, Ø, an 'oh' with a diagonal slash through it to distinguish it from the letter. You can see the null symbol over the letter 'P' here: http://www.flickr.com/photos/ajmexico/2766045525/#/photos/ajmexico/2766045525/lightbox/

(Teletypes only used capital letters, btw, which is why you don't see a "caps lock" key.)