Diminutive from 'iysh; the little man of the eye; the pupil or ball; hence, the middle (of night) -- apple (of the eye), black, obscure.
see HEBREW 'iysh
H380. ishon
אִישׁוֺן noun [masculine] pupil of eye (compare DlHA 9 PrätLoPh, Feb. 1884, but also Arabic , & NöZMG 1886, 739) — ׳א all construct — ׳א עַיִן Deuteronomy 32:10; Proverbs 7:2; ׳א בַּתעַֿיִן Psalm 17:8 (in all, simile of preciousness); = middle, midst of night ׳בְּא וַאֲפֵלָה לַיְלָה Proverbs 7:9; ׳בְּא חשֶׁח 20:20 Kt i.e. in deep darkness (Qr בֶּאֱשׁוּן see Now).
אִישַׁי see יִשַׁי.
אֱשׁוּן Qr Proverbs 20:20 see אִישׁוֺן below אישׁ.