P.Lond.Lit. 207 and the origin of the nomina sacra: a tentative proposal

The origin and development of the nomina sacra (sacred names written in an abbreviated form) found in early Christian texts is much debated in scholarly circles and no agreement has been reached. However the use of the nomina sacra in P.Lond.Lit. 207 may help to resolve some of the questions that surround the puzzle of their origin. P.Lond.Lit. 207 is a portion of papyrus that has broken off from a roll (24.5 X 25.7 cm), covering Psalms 11(12):7 to 14(15):4. The scribe of P.Lond.Lit. 207 has consistently written Kurios in an abbreviated form (nomen sacrum), giving only the first and last letters, and a supralinear bar drawn above the abbreviation. On the other hand, Theos is always written uncontracted. This is quite unusual given that Theos in Christian texts is always written as a nomen sacrum. Could the reason for this practice in P.Lond.Lit. 207 be found in the Semitic custom of contracting personal names to the first and last letter? Is Kurios abbreviated in this Semitic fashion to notify the reader that the word is being used to translate the personal name (the Tetragrammaton) of the Hebrew deity?