The question as posed by OP -- concerning aspects of the "πολύσπλαγχνος + οἰκτίρμων" pair in James 5:11 -- has all the seeds of its own answer. First, the relevant bit of text:
NA28 ... πολύσπλαγχνός ἐστιν ὁ κύριος καὶ οἰκτίρμων.
NRSV ... the Lord is compassionate and merciful.
I'll take the interrelated sub-questions in a slightly different order.
(1) Does their combination reflect any similar pairing in Hebrew?
Yes, it does. In Exodus 34:6 there is the famous statement:
MT: יְהוָה יְהוָה אֵל רַחוּם וְחַנּוּן אֶרֶךְ אַפַּיִם וְרַב־חֶסֶד וֶאֱמֶת
Heb: yhwh yhwh, ʾēl raḥûm wĕḥannûn, ʾerek ʾappayim, wĕrab-ḥesed weʾĕmet
Trans: The LORD the LORD, a God merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness
In the LXX the relevant pair looks like this:
LXX: ... οἰκτίρμων καὶ ἐλεήμων ...
That pairing ("compassionate and merciful") is applied to God 10x in the LXX with a reflex in the Hebrew text (MT): Exod. 34:6; 2 Chr. 30:9; Neh. 9:17, 31; Ps. 86:15; 102:8; 111:4;* 145:8; Joel 2:13; and Jon. 4:2. It also occurs Ecclesiasticus 2:11, where this "confession" appears in full. Of the total 12 occurrences, 5x οἰκτίρμων comes first, and 7x ἐλεήμων comes first.
* + Ps 112:4, used of the one who fears the LORD, in parallel to 111:4. Numbers in square brackets are LXX Psalm numbers.
As noted by OP, the word in the James 5:11 pair is the unique (in the LXX and NT) πολύσπλαγχνός rather than the typical member from the LXX, ἐλεήμων.
According to Moulton and Milligan's entry for πολύσπλαγχνός1 it is the equivalent of πολυέλεος in the LXX,2 "very merciful" (πολυ "much" + έλεος "mercy"), so closely related to ἐλεήμων.
(2) What detailed explanation can be given for the related meanings of these two words?
Any OP who can pose a question so thoughtfully ought to be able to go a good distance on this already.
;) But here are some quick thoughts based partly on observation of the text (where it starts, after all), and partly from quick checks in Jenni & Westermann (eds), Theological Lexicon of the Old Testament [TLOT], and the venerable Kittel & Friedrich (eds), Theological Dictionary of the New Tesatment [TDNT].
The theological nuance of the Hebrew pair, raḥûm wĕḥannûn, can be teased apart this way:
- raḥûm carries the sense of pardon or sparing, i.e. mercy where wrath might have been present; while
- ḥannûn is the king's gracious and beneficent presence with his people for good.
Stoebe's article (רחם, TLOT, 3.1227; he also did the חנן article) emphasizes the frequency with which these occur together as a liturgical saying. I can only find two occurrences each where they appear without the other (raḥûm "alone": Deut 4:31; Ps 78:38; and ḥannûn "alone", Exod 22:27[v. 26 in Heb], but Ps 116:5 includes raḥēm).
In Greek. the pairing works this way (with typical Hebrew counterpart):
- ἐλεήμων (ḥannûn) is merciful compassion; while
- οἰκτίρμων (raḥûm) is sympathy, pity, involving compassionate intervention.
If there is some sense of confusion at this point, that is probably a good thing. The history of the use of these terms is deeply intertwined, with the σπλαγχν- group -- which in earlier Greek usage simply had its literal sense (normally) of "innards" before being used as a translation equivalent for raḥûm in the LXX (with its own literal meaning of "womb") -- beginning to displace οἰκτίρμων in some measure (cf. Koester, TDNT, 7.550-553). Within that group is James 5:11's πολύσπλαγχνος.3 These terms have their own development in Greek, apart from the related Hebrew vocabulary, and it is ἐλεήμων that is "displaced", rather than οἰκτίρμων.
And so, having said all that...
(3) Is there a meaningful distinction between them?
Probably not. One can see more meaningful distinctions between the underlying Hebrew terms, but even in the Tanakh they tend to appear as a set-pair. By the time you get to the inter-related use of the terms in Greek, with their dependence on the LXX and in some sense a "liturgical" use, then Bultmann's contention (TDNT, 5.161) that they form a sort of hendiadys makes very good sense, emphatically expressive of "heartfelt compassion".4
- James Hope Moulton & George Milligan, The vocabulary of the Greek Testament illustrated from the papyri and other non-literary sources (Hodder & Stoughton, 1914-1929), p. 527:
"very pitiful." This word, confined in the NT to Jas 5 11, is said to be found elsewhere
only in Hermas Mand. iv.3.5, Sim. v.7.4. It is the equivalent of the LXX πολυέλεος
(Ps 102:8). See s.v. σπλάγχνον.
Before anyone jumps on my citation of this old reference work, please read Larry Hurtado's panegyric. Thank you.
- Used 11x - Exod. 34:6; Num. 14:18; Neh. 9:17; 3 Ma. 6:9; Ps. 85:5, 15; 102:8; 144:8; Odes 12:7; Joel 2:13; Jon. 4:2 (all LXX references).
- There are about a dozen (maybe a few more) uses in the post-apostolic and later literature (e.g., Shepherd of Hermas, Clement of Alexandria, in the Acts of Thomas).
- The few modern commentaries I've consulted aren't especially interested in the phrase per se. See, however, J.H. Ropes, A critical and exegetical commentary on the Epistle of St. James (T & T Clark, 1916), pp. 299-300 for some useful comment.