Conceptual Inertia posted a good answer on parallelism and hapax legomena. But just to add a couple of points:
Dr. Chaim Cohen (Biblical Hapax Legomena in the Light of Akkadian and Ugaritic, 1978) observed that the Hebrew "שפרה" is a possible cognate of the Akkadian "šaparru" (meaning "net"). However, this does not imply that the two words share the same meaning. Often, the definitions of cognates diverge in their respective languages, including Semitic languages as closely related as Hebrew, Akkadian, and Ugaritic.
As Rashi1 and the Metzudas David observe in their commentaries on Job 26:13, "שִׁפְרָה" bears a similarity with the Hebrew word "שפריר" (a noun meaning "canopy", cf. Jeremiah 43:10, "וְנָטָה אֶת שַׁפְרִירוֹ") and may be a pi'el conjugation ("He canopied the heavens"). There's a degree of similarity in meaning between "canopy" and "net" that is consistent with what you'd expect of Semitic cognates.
It seems Cohen disregarded this and chose to simply apply the precise Akkadian translation of "šaparru" directly to the Hebrew in
Job 26:13. Professor Naftali Herz Tur-Sinai took this further and suggested splitting שמים into two words (שָׂם יָם), which he felt would make the verse more consistent with Cohen's translation:
ברוחו שם ים שפרה
Which Prof. Tur-Sinai interprets to mean:
With His wind, He caught the sea in His net
There are a number of problems with this, however. First of all, this emendation appears highly speculative. It is ostensibly motivated to by a preference for associating a net with the sea rather than the heavens (which presupposes that Cohen's translation of "net" is compelling, which it is not), as well as a desire to impose a polytheistic Levantine mythological milieu onto Job.
Secondly, Tur-Sinai's hypothesis would require that שפרה also be emended to "בְּשִׁפְרָתוֹ" as a noun with a prepositional prefix and possessive suffix. None of this is indicated in the text.
Thirdly, Akkadian has many different words for "net", and "šaparru" carries the sense of a net used for transporting something over land rather than for catching something or for use in the water.
Incidentally, Tur-Sinai's use of the past participle "שָׂם" ("placed" or "put") seems a bit unusual in this context. In Biblical Hebrew, when "שָׂם" or other conjugations of its root operate on large features of geography or nature (the land, the sea, the sky, countries, cities, etc.), and specifically when those features are the direct object of an independent clause, they typically mean "made" or "transformed" rather than "placed" or "put" (e.g., "Who made [שָׂם] the whole world?" Job 34:13, where "world" is the direct object2).
By contrast, when describing the Almighty's physical movement of these large features of geography, the verses tend to employ a variegated assortment of different verbs, some of which appear in this very chapter (26) of Job ("נֹטֶה צָפוֹן", "תֹּלֶה אֶרֶץ", "רָגַע הַיָּם") and elsewhere ("הַמַּעְתִּיק הָרִים" in 9:5, "הַמַּרְגִּיז אֶרֶץ מִמְּקוֹמָהּ" in 9:6, "נֹטֶה שָׁמַיִם" in 9:8, as well as other conjugations of נתן, שלח, רקע, etc.). If Job 26:13 is indeed describing placing the sea into a net, one might have expected some such verb to appear. Alas, it does not.
Finally, the word "שָׁמַיִם" ("heavens") that appears in the Masoretic text of Job 26:13 also shows up hundreds of times throughout the Bible. On the other hand, there are zero Biblical appearances of word pair ("שם ים") with which Tur-Sinai wishes to replace it. This itself renders Tur-Sinai's emendation improbable.
Professor Tur-Sinai's approach to this verse seems to require a lot of unnecessary tinkering. Even if one insists on using Cohen's speculative translation of "שפרה" as "net", it would be far less linguistically problematic to just use it as is ("With His wind, the heavens are a net"3) and leave the text alone.
1Note that Rashi (on Job 26:12 and Isaiah 27:1) identifies both "רָהַב" and "נָחָשׁ בָּרִחַ" as allegorical references to Egypt, the former based on the identification provided by Isaiah 30:7 ("וּמִצְרַיִם הֶבֶל וָרִיק יַעְזֹרוּ לָכֵן קָרָאתִי לָזֹאת רַהַב הֵם שָׁבֶת")
2As opposed to where the large geographical feature is the indirect object, as in Psalms 89:26, where the meaning is "placed"
3Cf. Isaiah 40:22, "הַנּוֹטֶה כַדֹּק שָׁמַיִם"