To nibble on something is to eat a tiny bit of it. People nibble at things to taste them, or because they don't want to eat a lot. Nibble can also be used as a noun, as in "Take a little nibble of this."
A nibble (sometimes spelled nybble) is also 4 bits, this is, half a byte. Being four bits, there are sixteen ( 24 ) possible values, and so a nibble is evenly representable by a single hexadecimal digit (thus often called a "hex digit"). A full byte is evenly representable by two hexadecimal digits; therefore it is a common way to display bytes of information as two hexadecimal nibbles. (Compare this definition of nibble with the one above; computer scientists have a tradition of giving things "punny" names.)
There is also the "Nibbles game." It is present today in many cell phones.\n