"The cave of Machpelah" (Genesis 23:9): Rav and Shmuel differed. One said it was two chambers, one within the other; and one said it was a chamber with an upper story above it. It is well according to the one who says one was above the other, for this is why it is written "Machpelah" [doubled, as in folded over]. But according to the one who says two chambers, one within the other, what is the meaning of "Machpelah"? That it was doubled with pairs [of those buried in it].
Why the Cave of Machpelah Is Called the Doubled Cave
Yalkut Shimoni on Torah 102:8
מְעָרַת הַמַּכְפֵּלָה, רַב וּשְׁמוּאֵל, חַד אָמַר, שְׁנֵי בָּתִּים זֶה לִפְנִים מִזֶּה, וְחַד אָמַר, בַּיִת וַעֲלִיָּה עַל גַּבָּיו. בִּשְׁלָמָא לְמַאן דְּאָמַר זֶה לְמַעְלָה מִזֶּה, הַיְינוּ דִּכְתִיב מַכְפֵּלָה, אֶלָּא לְמַאן דְּאָמַר שְׁנֵי בָּתִּים זוֹ לִפְנִים מִזּוֹ מַאי מַכְפֵּלָה, שֶׁכְּפוּלָה בְּזוּגוֹת.