Please explain how this operator overloading works.

[440bx]

3. The term itself was introduced in 1965 by John G. Kemeny in 1965, who was wrong because it already existed under different names all the way back to Boole himself.

Do you have references for those events ?

After some googling, it seems the term "nibble" was coined by IBM when they went from their 6 bit machines to 8 bit machines.  The "byte" was therefore 8 bits and, half a byte, 4 bits, was deemed a nibble.

Since 8 bits has pretty much become the standard number of bits in a byte, the nibble has consequently pretty much become 4 bits.

(if a manufacturer decided to create a 9 bit byte, it will be "interesting" to see what they do about a "nibble")

[af0815]

Philips have PLCs (PC20, maybe PC10) running with 4 Bit CPUs inside in 1980. And there i have learned the Name 'nibble' and two nibbles (NOT nipples) are one byte.
The P850 Minicomputers are working with four nibbles, because this computer was a 16 Bit one, called one word (since 1971). http://bitsavers.trailing-edge.com/pdf/philips/brochures/P850_P855_P860_Brochure_1971.pdf 

[Warfley]

No, it is - with different wording . It is just that in CS it is defined often as half a byte (4 bits) which is wrong since Leibnitz , not Boole, and even I Ching many moons before that, defined what we now call Boolean arithmatic and both explained the importance of a half value..

If a word is used a certain way, it cannot be wrong. This is the only rule of linguistics, it is always descriptive, never prescriptive. You can say how a word is used, but not how a word should be used.

It's a bit different with respect to scientific definitions in a certain context. For example, as you mentioned boolean arithmetic, the very first definition of my discrete maths class at university was the definition of logical formulas, which included a specific defintion for the terms "boolean constant" and "boolean function". So when I would be in that class and claim that 1 is the boolean constant representing the value "false", I'd be wrong according to the definitions set out earlier in that class. But only in that context because of this definition.
For example in the context of bash scripting, exit codes are used to evaluate logical operations, where 0 means true and any other value represents false. There the defintions of my discrete maths course do not hold, because in this context the definitions made by the POSIX standard are used for describing the properties of the language.

Long story short, the term Nibble is mostly used to describe half-bytes, and this is completely correct in these times. Thats just how language works

[Thaddy]

Do you have references for those events ?

Yes, as I already added them. First CS mention was in 1959, not 1966 (found that out later after a ping from a collegue). First theory by I Ching and in western literature Leibnitz.
Furthermore, the possibility for uneven nibbles was also discussed.
Anyway: I - and/or Avra, I think we both touched that code -  implemented the helpers along the way of what is generally understood by normal people to use 4 bit nibbles even if it is wrong. ARM got it right, though.
The wikipedia entry is also not correct and I will ask for discussion and review.
Anyway does not matter, since even I consider a nibble to be implemented as half a byte. (Which is wrong, but right  )

[440bx]

Do you have references for those events ?

Yes, as I already added them. First CS mention was in 1959, not 1966 (found that out later after a ping from a collegue). First theory by I Ching and in western literature Leibnitz.
Furthermore, the possibility for uneven nibbles was also discussed.

ok... you claim to have references and have already "added" them... but... could you post them for other people to benefit from them ?

[Thaddy]

References with detailed explanation:

The term "nibble" or "nyble" originated in the 17th century with Gottfried Wilhelm Leibniz, a German philosopher, mathematician and scientist. He introduced the concept of the binary number system in his "Explication de l'Arithmetique Binaire" (1703) in which he defined a "nyble" as a unit of binary information. This type of binary representation had been previously used in ancient Chinese divination, where the I Ching (Book of Changes) contained a system of 64 hexagrams which could be interpreted with the help of a binary system.

I could not find a direct association with size other than the ARM manual, but I am sure it is there.

[Solecist]