Wilfred G.E. Watson writes in ["The Hebrew Word-pair *'sp // qbṣ*"](http://dx.doi.org/10.1515/zatw.1984.96.3.421) (Zeitschrift für die Alttestamentliche Wissenschaft 1984, 96(3)):

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> Before going on to consider the word-pair in question it is necessary to establish which is the A-word, and that in turn involves setting out the 'family' of word pairs belonging to the *'sp-qbṣ* group, but featuring only one component of the pair
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What follows is a table of four lists of occurrences:

* where אסף is the "A-word" with some other verb (presumably as B-word); denoted "'sp //     "  

(e.g. Ez. 34:29, Koh. 2:26, Isa. 17:5, Num. 21:16)
* where קבץ is the "B-word" with some other verb (presumably as A-word); denoted "     // qbṣ"  

(e.g. Isa. 43:5, Prov. 13:11, Ez. 20:34, Joel 4:2)
* where אסף is the "B-word" with some other verb (presumably as A-word); denoted "     // 'sp"  

(e.g. Isa. 60:20, Dan. 11:10, Isa. 58:8, Isa. 32:10)
* where קבץ is the "A-word" with some other verb (presumably as B-word); denoted "qbṣ //     "  

(e.g. Isa. 49:18, Isa. 44:11, Hos. 9:6, Jer. 49:14)

What are A-words and B-words in biblical hermeneutics (or linguistics, in which case this question could perhaps be migrated)? Does it only indicate that the A-word occurs chronologically / syntactically before the B-word (and the two words are on the same syntactic level) or does it indicate some hierarchy, where the B-word would be dependent on the A-word: syntactically, pragmatically or rhetorically?

I have not been ably to find any other mention of these terms nor an explanation of what they mean (searching is complicated because search engines turn "A-word" into "a word" and "B-word" has another meaning).