Singular or plural?

Could some one establish that the KJV rendering "oath's" (singular possessive in English) corresponds to a plural form of horkos from the TR Greek text? Matthew 14:9 and parallel verse in Mark 6:26 --

And the king was sorry: nevertheless for the oath's sake, and them which sat with him at meat, he commanded [it] to be given [her].

And the king was exceeding sorry; [yet] for his oath's sake, and for their sakes which sat with him, he would not reject her.
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Maybe. But a statement found in Wikipedia --

The use of the apostrophe to mark the English possessive ultimately derives from the Old English genitive case, indicating possession; this often ended in the letters -es, which evolved into a simple s for the possessive ending. An apostrophe was later added to mark the omitted e, a practice that came into general use in the 17th century... ​

I checked a source for the 1850 revision of the KJV and it was still "oath's" (singular possessive) in both occurrences. I also looked at nine other TR-based texts: the King James Bible Clarified (1998, McGinnis), the King James Version Hebrew Names Edition (1999, Cummings), the American King James Version (1999, Engelbrite), the Third Millenium Bible (1998, Deuel Enterprises), the 21st Century King James Version (2003, Deuel Enterprises) and found them all still having "oath's" (singular possessive) in both verses. {Evidently, this is a modern-day sickness.} The AV7 (2008, The New Authorized Version Foundation) had both occurrences in the singular form!

Young (1862) and Darby (1890) both have "oaths" (plural). So does the LITV (1976-2000, Green) --

And the king was grieved, but because of the oaths, and those who reclined with him, he ordered it to be given. (Matthew 14:9)

And having become deeply grieved, but because of the oaths and those reclining together, the king did not wish to reject her. (Mark 6:26) ​

 

I still want some help from the Greek 'experts' because I also see where some other versions have rendered this word as singular (like the NET, NLT, and Webster). Notice A.T. Robertson's note at Matthew 14:9 --

... Herod, however, shrank from so dastardly a deed as this public display of brutality and bloodthirstiness. Men who do wrong always have some flimsy excuses for their sins. A man here orders a judicial murder of the most revolting type "for the sake of his oath"...​

There is a variation between the Stephen's 1550 text (dia de tous orkous) and the Wescott-Hort text (dia tous orkous). Does the presence of de affect the number in translation in some manner?

 

Thanks, TCGreek! Of course we're going with the Greek; Greek is the basis for all other NT texts.

 

So, while the AV text may not have been in error in 1611 (given the benefit of any doubt), it was a mistake to have not been fixed in later revisions. Any contemporary reader of a KJV would understand "oath's" to be the ordinary singular possessive; yet, thisdoes not accurately represent the plural form of the underlying Greek texts (and probably is not the AV translators' intended meaning of the possessive plural in English). But should we have to appeal to the Greek to discover what is God's word?

In the context of today's English the rendering of "oath's" is just plain wrong. This archaic plural form of "oath's" would not be available in a dictionary; this obsolete plural form of "oath's" is not discussed in commentaries. Is the Holy Spirit expected to miraculously lead all readers into the obscured truth of "oath's" in the KJV? Is this really the best text that can be provided?

Matthew 14:9 and parallel verse in Mark 6:26 --

And the king was sorry: nevertheless for the oath's sake, and them which sat with him at meat, he commanded [it] to be given [her].

And the king was exceeding sorry; [yet] for his oath's sake, and for their sakes which sat with him, he would not reject her.
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