‘Zib’ is a nonsense word without prior meaning in English, chosen somewhat arbitrarily for its similarity (in length, sound, and spelling) to bit, while also being sufficiently distinct.
As it turns out, though, alternate derivations can be chosen retroactively. A recursive backronym is one possibility:
ZIB = ZIB Is Bitcoin - emphasizing that this is just another convenience denomination of Bitcoin itself.
Also, ZIB was the name given to a stray dog drafted by the Soviet space program in 1951 for a suborbital test flight. (Apparently ZIB made it back successfully.) Since many cryptocoin enthusiasts like the idea of dog mascots going to the moon, why not honor a common mutt that’s been closer to the moon than any purebred?
People are already using the terms ‘millibits’ and ‘microbits’ (or ‘eubits’) as natural shortenings of ‘millibitcoins’ and ‘microbitcoins’, respectively. Using ‘bit’ to refer to the same thing as ‘microbit’ presents problems. (As just one example, the bitcoin-derived 1/1000th fraction some have already been calling a “millibit” and the new ‘bit’-derived 1000X multiple “kilobit” would be… the exact same unit.)
Also, ‘bit’ already has an archaic meaning in money (1/8th of a dollar) and very current and prominent meanings within the Bitcoin system, as the binary digits and basic units of information in its hashes, cryptographic keys, and protocol. Those kinds of bits represent information, are indivisible, and fit 8-to-a-byte, 16-to-a-word, etc. To the implementors of bitcoin, a phrase like “1000 bits” has a strong meaning, enough information to store a value up to 2^1000, and not a count of 1000 things-called-bits. (Such a count would fit into just 10 bits, since 1000 < 2^10.)
And if a ‘bit’ is 100 satoshi, then literally reading “bit-coin” would make one think of a “100 satoshi coin”. But of course the unit “bitcoin” actually means a value 1 million times as large, 100,000,000 satoshi.
So while ‘bit’ is catchy, it jumps into a semantic blender in relation to other key bitcoin concepts. It’d be hard to bootstrap as a term, and prone to confusing people for the entire duration of its use. (“What do you mean, my 256-bit private key? It should have thousands of bits in it!”)
‘Zib’ was specifically chosen to match the compactness and general sound/lightness of ‘bit’, but without overloading the term with yet another contrasting meaning. While novel, it’s about as easy to say or spell. ‘Zib’ also works better as a verb (“Could you please zib 10,000 to me?” compared to “Could you please bit 10,000 to me?”), because there’s no comprehension-interference with the past-tense of “bite”. (“He bit you 10,000 times? Did it leave marks?”)
Of prior proposals, that’s one of the best – but still has problems.
It requires the secondary spelling (“mike”) to clarify pronounciation. There will be a natural tendency to abbreviate it with an ‘m’ – which risks confusion with ‘millis’, a very different unit. Using the proper metric abbreviation, µ (“mu”), then just makes things seem more arcane. Since it still references micro-, it still risks confusion with milli-, and still implies something that is tiny and perhaps invisible or ignorable.
It may invite the questions, “Who’s Mike? Is there a Mike Nakamoto, perhaps Satoshi’s long-lost son, brother, or father?”
Comparatively, ‘zib’ or ‘Z’ can be unambiguously communicated, and used consistently across both formal software and casual conversation.
XBT, that’s gaining momentum as a currency-code?
Zibcoin may be a better unit for quoting currency exchange rates, too, by avoiding deep-decimal values over certain expected quoting ranges. If needed, the currency-code
XZB appears to be available.
(contribute more questions/answers via zibcoin.org github project)