yashfeh and diaper

In Shemot 28:15-20, there is a description of the breastplate of the high priest - the choshen mishpat. The breastplate contained 12 stones, in four rows of three. 

The identities of many of the stones listed are highly debated. It's very difficult to find two translations that render each of the stones in the same way. But one stone almost always gets the same translation, the yashfeh יָשְׁפֵה of Shemot 28:20. All the English translations I consulted had it as "jasper."

This should not be surprising, as the English word "jasper" very likely derives from yashfeh or a cognate Semitic word. Here's the Online Etymology Dictionary entry for jasper:

precious stone, c. 1300, from Anglo-French jaspre, Old French jaspre, with unetymological -r-, a variant of jaspe (12c.), from Latin iaspidem (nominative iaspis), from Greek iaspis "jasper," via an Oriental language (compare Hebrew yashpeh, Akkadian yashupu).

Klein has a similar entry for yashfeh:

Probably borrowed from yashupū (also ashpū), whence also Syriac יָשְׁפֵה, יַשֽׁפָא, Persian yashm, whence Arabic  yashb (= jasper). Greek. iaspis, whence Latin iaspis, is a Sem. loan word.

All of this isn't so surprising. Gems were rare, and so it makes sense that they would retain the name from where they came. However, the next development surprised me.

In Klein's CEDEL, he has the following entry for the word "diaper":

Middle English diaper, diapery from Old French diapre, from earlier diaspre (whence French diapre, 'diapered, variegated'), from Middle Latin diasprum (whence also Italian diaspro, Old Provencal diaspre, Spanish diaspero, Portugese diaspero, diaspro), 'jasper', from Latin iaspis, from Greek iaspis, 'jasper', ultimately from Hebrew yashpheh

I suppose I can see how the words are similar (although he doesn't explain where the added "d" comes from), but what is the connection between the meanings of "jasper" and "diaper"?

This site, quoting Webster's New World College dictionary, provides a possible explanation:

ME < OFr diapre, diaspre, kind of ornamented cloth < ML diasprum, flowered cloth, altered (after dia-, dia-, because of ML pronun. of initial j-) < jaspis < L iaspis, jasper

So it seems that the connection here is that just like jasper is an ornamental gem, diapers were originally ornamental cloth. A different gem actually appears in the first (archaic) definition that dictionary provides:

1.
a.  Archaic: cloth or fabric with a woven pattern of repeated small figures, such as diamonds
b. a napkin, towel, etc. of such cloth
c. such a pattern, as in art
2. 
a. a soft, absorbent cloth folded and arranged between the legs and around the waist of a baby to absorb and contain excretions
b. a piece of absorbent material with a waterproof outer layer, having the same function but intended to be discarded after a single use

It's interesting to see how the meaning of diaper progressed to an item of less and less value - from a fancy ornamented cloth, to a cloth in general, to a cloth used to wrap around babies, to the disposable kind popular today.

I'm just still not sure I understand why it begins with "d." For that, perhaps its worth looking at the Online Etymology entry for diaper. While they don't accept the "jasper" connection, they do say that the prefix "dia-" meant "thoroughly, interspersed", which could apply to the gem shapes (jasper) as much to the "white" that they suggest:

mid-14c., "costly silken fabric of one color having a repeated pattern of the same color woven into it," from Old French diapre, diaspre "ornamental cloth; flowered, patterned silk cloth," perhaps via Medieval Latin diasprum from Medieval Greek diaspros "thoroughly white," or perhaps "white interspersed with other colors," from dia "thoroughly" (see dia-) + aspros "white."

Now while the choshen was in fact a fancy woven cloth with stones interspersed, I don't recommend you call it a "diaper" unless you're willing to face some serious questions...