Nybble

(alt. 'nibble') [from v. 'nibble' by analogy with 'bite' => 'byte']

n. Four bits; one hex digit; a half-byte. Though 'byte' is now techspeak, this useful relative is still jargon.

Compare byte, crumb, tayste, dynner; see also bit, nickle, deckle. Apparently this spelling is uncommon in Commonwealth Hackish, as British orthography suggests the pronunciation /ni:'bl/.