Presumed to be the "constructive" or genitival form of -av {av}; short for 'avvah; desire (and so probably in Prov. 31:4); hence (by way of alternative) or, also if -- also, and, either, if, at the least, X nor, or, otherwise, then, whether.
see HEBREW 'avvah
H176. o
אוֺ320 , , ),
conjunction or (whether aut or vel).
1 Genesis 24:49; 31:43; Exodus 4:11; Song of Solomon 2:9; Leviticus 13:24; Numbers 5:30 + often (especially in laws); sometimes implying a preference, nearly = or rather Genesis 24:55 עָשׂוֺר אוֺ יָמִים a few days or ten Judges 18:19; 1 Samuel 29:3. Prefixed to the first as well as to the second alternative (rare) either (whether) ... or Leviticus 5:1; 13:48, 51; = or, if not Ezekiel 21:15 (si vera lectio) Ke Malachi 2:17; Job 16:3; 22:11.
2 introducing a sentence, especially a particular case under a General principle, or = or if Exodus 21:31 וג יִגַּח ׳אוֺבֵֿן or if he gore a son, etc. 21:36; Leviticus 4:23, 28 (see Di) Leviticus 5:21; Leviticus 5:22; 25:49b; Numbers 5:14; 2 Samuel 18:13 or if I had dealt falsely against his life, then, etc., Ezekiel 14:17, 19 or if I send, etc.
3 if perchance, 1 Samuel 20:10 if perchance thy father answer thee with something hard, Leviticus 26:41.
4 once, with the jussive (as in Arabic with the subjunctive see Dr§ 175) = except: Isaiah 27:5 I would burn them together, בְּמָעֻזִּי יַחֲזֵק אוֺ or else let him take hold (= except he take hold) of my strong-hold, etc.
אוּ Proverbs 31:4 Kt, see [אַי].
[אַו] noun masculine construct אוֺ, Kt Proverbs 31:4 desire, so Thes MV; but < Qr אֵי q. v.