Q&A: What is a biblical Hebrew expression that hardly anyone is familiar with – or even knows what it means?

My favourite so far is לֹא אָבָה יַבְּמִי – lo avah yabmi (Deut. 25:9)—meaning ‘He will not perform the duty of my husband’s brother’—which is the official complaint of a childless widow whose brother-in-law refuses to do his fraternal duty of giving her a child after the husband has died.

Source: https://images.app.goo.gl/7rj642DevKTEgnS48

The expression is unfamiliar because the word yabmi is a conjugation of a curious verb— לִבְּמוֹת libmot — which is awkward to pronounce, not used in other contexts, and even the word for husband’s brother (יבם yavam), is unfamiliar today (in modern Hebrew, it is גיס gis, and can refer to the wife’s brother, as well).

I also love the description of the consequences of such a refusal:

ז וְאִם-לֹא יַחְפֹּץ הָאִישׁ, לָקַחַת אֶת-יְבִמְתּוֹ; וְעָלְתָה יְבִמְתּוֹ הַשַּׁעְרָה אֶל-הַזְּקֵנִים, וְאָמְרָה מֵאֵן יְבָמִי לְהָקִים לְאָחִיו שֵׁם בְּיִשְׂרָאֵל–לֹא אָבָה, יַבְּמִי. ח וְקָרְאוּ-לוֹ זִקְנֵי-עִירוֹ, וְדִבְּרוּ אֵלָיו; וְעָמַד וְאָמַר, לֹא חָפַצְתִּי לְקַחְתָּהּ. ט וְנִגְּשָׁה יְבִמְתּוֹ אֵלָיו, לְעֵינֵי הַזְּקֵנִים, וְחָלְצָה נַעֲלוֹ מֵעַל רַגְלוֹ, וְיָרְקָה בְּפָנָיו; וְעָנְתָה, וְאָמְרָה, כָּכָה יֵעָשֶׂה לָאִישׁ, אֲשֶׁר לֹא-יִבְנֶה אֶת-בֵּית אָחִיו. י וְנִקְרָא שְׁמוֹ, בְּיִשְׂרָאֵל: בֵּית, חֲלוּץ הַנָּעַל.

7 And if the man like not to take his brother’ wife, then let his brother’s wife go up to the gate unto the elders, and say, My husband’ brother refuseth to raise up unto his brother a name in Israel, he will not perform the duty of my husband’ brother. 8 Then the elders of his city shall call him, and speak unto him: and if he stand to it , and say, I like not to take her; 9 Then shall his brother’s wife come unto him in the presence of the elders, and loose his shoe from off his foot, and spit in his face, and shall answer and say, So shall it be done unto that man that will not build up his brother’ house. 10 And his name shall be called in Israel, The house of him that hath his shoe loosed.

Would make a great Israeli Jeopardy! question (if such a show existed)—or failing that, for any Bible contest.