The dominant modern account of אַבְרָהָם is Albright's: the longer form is an Aramaic-style dialectal expansion of אַבְרָם, a secondary ה inserted in a mediae waw root, a pattern attested elsewhere (Heb. רוץ beside Aram. רהט, to run; Heb. בוש beside Aram. בהת, to be ashamed). Van Seters confirmed the phenomenon as characteristic of Aramaic and South Arabic, and Sarna and Sperling summarize the consensus in the Encyclopaedia Judaica as a mere dialectic variant of Abram. On this reading the two forms originally meant exactly the same thing, so the underlying sense remains the West Semitic Satzname analyzed since Noth as ab (a kinship term used as a divine title) plus the stative ram from רום: the (divine) Father is exalted. Two older solutions for the added element survive as minority positions. Lexicographers from Hottinger through Gesenius, followed by Keil and Delitzsch, invoked Arabic ruham (numerous) to preserve father of a multitude as a genuine etymology, an option Albright himself cautiously entertained as a possibly obsolete Hebrew cognate; ruham is rare even in Classical Arabic and postdates biblical Hebrew, so few now defend it. Hommel, on South Arabian orthographic analogies, held that the two forms are genuinely distinct names with the longer independently meaning father of a multitude, a view preserved in the older ISBE and discussed by Fleishman.
On Gen 17:5 itself there is near-consensus among commentators (Sarna, Speiser, Westermann, von Rad, Wenham, Hamilton, Cassuto, Vawter, Skinner) that אַב הֲמוֹן גּוֹיִם is paronomasia, a Volksetymologie, rather than philological derivation: the phrase contains no ר to match the ר of the name, and no Hebrew root רהם meaning multitude is attested. Hamilton's formulation is representative, that the etymology is neither the literal nor the etymological meaning but is phonemically similar to ab hamon. Wenham and Strus note that Gen 17:1-8 is saturated with terms whose consonants echo the new name (בְּרִית, רבה, פרה), making the passage an artful sound-play. Genesis 17 is among the most securely Priestly chapters in source criticism, from Wellhausen through Noth, von Rad, Westermann, Speiser, and Van Seters, and for P the renaming is programmatic: it coincides with the אֵל שַׁדַּי theophany, the בְּרִית עוֹלָם, and the institution of circumcision. Sarna observes that name-giving in the ancient Near East was an act of sovereignty (compare Neco renaming Eliakim as Jehoiakim, 2 Kgs 23:34), and Westermann calls the new name a Verheissungszeichen, a sign of promise, since the still childless patriarch must proclaim the promise whenever he names himself. Fokkelman and Sarna place the renaming at the temporal midpoint of the Abraham cycle, twenty-four years after the call and one year before Isaac's birth.
The distribution is disciplined and is itself an argument. אַבְרָהָם occurs about 175 times, overwhelmingly in Gen 17-50 and then scattered through Exodus, Leviticus, Numbers, Deuteronomy, Joshua, Kings, Chronicles, Nehemiah, Psalms, Isaiah, Jeremiah, Ezekiel, and Micah, while אַבְרָם is confined to Gen 11:26-17:5 with only 1 Chr 1:27 and Neh 9:7 reaching back for it. The redactional discipline is not source-based: both J and P material use the short form before Gen 17 and every source uses the long form after it, which is why Westermann calls the chapter the literary and theological climax of P's Abraham cycle. Parallel renamings cluster in the same material (Sarai to Sarah in the same chapter, Jacob to Israel at Gen 32:28 and 35:10), and Moberly reads them as one theological pattern in which the new name declares a divine reality already true but not yet visible. Bereshit Rabbah 47.1 and Rashi observe that the ה added here and the ה of Sarah with the yod that leaves Sarai spell יָהּ. Later Israel remembers only the renamed patriarch, as יהוה אֹהֲבִי in Isa 41:8 and again in 2 Chr 20:7, and Levenson stresses that the universal fatherhood embedded in the new name is what makes Abraham the shared patriarch of Judaism, Christianity, and Islam. Of the external parallels, only the Middle Kingdom Egyptian Aburahana of the Execration Texts has been proposed for the longer form, and Rainey's re-reading as Abu-la-hana has left the identification disputed.