I'd add the Book "Encountering the Manuscripts: An Introduction to New Testament Paleography & Textual Criticism" by Philip Comfort to Mr Penner's list. He has a whole chapter of the book dedicated to a discussion on the NS, pp. 199-254.
I'd also recommend Larry Hurtado's blog at http://larryhurtado.wordpress.com/
as he usually has some great stuff on the Nomina Sacra, as well as his book "The Earliest Christian Artifacts" Chapter 3 pp.95-134.
Other words like καί are also abbreviated with ligatures.
Looking at most of the 70+ pre-300 Greek NT Papyri, και is actually very rarely abbreviated among them. I find και abbreviated to ϗ in Papyrus 12 (which is effectively the top of a letter containing only Heb 1:1); Papyrus 16 (only in Phil 3:17, at the end of a leaf); Papyrus 66 (used in John 1:10, 21, 25, 45, 46, 48; 2:2; 3:11, 12, 22; 4:30, 38, 47; 5:30; 6:40, 42, 45, 63, 70; 7:11, 12, 36; 8:21, 25, 32, 50, 56; 9:15; 10:9, 10, 28, 35; 11:31, 33, 34, 37, 43, 48; 12:18, 28, 34; 13:31, 32; 14:19, 22; 16:14, 22, 26, 27; 17:19; 18:33; and conjectured to be in 21:11); and finally in Papyrus 75 (only in Luke 24:35).
As can be quite clear from above, it seems that only one pre-300 Greek NT manuscript abbreviated και more than a couple of times, and then, not unanimously.
Other words like καί are also abbreviated with ligatures. I think most of these words fall into the 'Frequent Word' category.
As Larry Hurtado notes in his book mentioned above, "With the nomina sacra
, however, it is usually the case that limitations of space are not a factor. As noted previously, the wide margins, generous line spacing, and usual size of the characters all indicate no concern whatsoever about conserving space or having to crowd text into a limited amount of space. Thus the nomina sacra
are not really abbreviations, at least in the sense that they do not function to save space or writing effort." (TECA, pp. 100).
So I don't think the Nomina Sacra were chosen because they were used frequently, especially when not all the words noted above were instantly used in their nomen sacrum form from the earliest evidence, nor were they always nomen sacrum in manuscripts where the Nomina Sacra are quite prevalent. Papyrus 75 for example seems to fluctuated between using the Nomen Sacrum for ανθρωπος, and writing out the word in full (See John 1:4 where [O]ανων[/O] appears, and then John 1:6 where ανθρωπος is written out in full).
David and Jerusalem both have variant spellings. Are there dative/accusative abbreviations?
For David and Jerusalem, or for the Nomina Sacra in general? For the NS in general, yes - for David and Jerusalem, the list of Nomina Sacra on wikipedia (compiled from The Text of the Earliest NT Greek Manuscripts by Philip Comfort and David Barrett), the only manuscripts to have Jerusalem as a nomen sacrum are Papyrus 50, and Uncial 0189, both of which only have it for the transliteration of the Aramaic form as [O]ΙΛΗΜ[/O].
Unfortunately I've yet to finish that for Papyrus 75, but thankfully Philip Comfort in "Encountering the Manuscripts" says: The scribe of P75 used a nomen sacrum for “Jerusalem” only in Luke, not in John. Furthermore, the nomen sacrum for “Jerusalem” in P75 is used only for the Greek transliteration of the Aramaic form, never the hellenized form. This could indicate that the scribe was simulating an earlier Greek Old Testament scribal practice. The scribe of P50 and the scribe of 0189 also used the nomen sacrum for the transliteration of the Aramaic form.
And not surprisingly, P. Comfort doesn't discuss the Nomen Sacrum for David, for as far as I can recall, Codex Sinaiticus is the earliest manuscript to use the Nomen Sacrum for David. Although I don't know for the pseudepigrapha/Apocrypha Greek NT Literature, which also used the Nomina Sacra, as did manuscripts containing writings from the ECF (an early manuscript containing Irenaeus' "Against Heresies" contains the Nomen Sacrum [O]XΣ[/O]. Unfortunately I can't remember the papyri's name).
Does anyone know whether the ECF mention the Nomina Sacra, or had they become so widespread, that an explanation of them wasn't effectively necessary for those in an around the early believers?