Probably from an unused root meaning to be prominent; properly, brightness (compare ziyv), i.e. (figuratively) the month of flowers; Ziv (corresponding to Ijar or May) -- Zif.
see HEBREW ziyv
H2099. Ziv
זִר apparently proper name of 2nd month, = approximately April-May, named as month of beginning the temple building; הַשֵּׁנִי הַחֹדֶשׁ הוּא זִו בְּחֹדֶשׁ 1 Kings 6:1 = זִ֑ו בְּיֶרַח 6:37; ᵐ5 B 6:1 has simply ἐν μηνὶ τῷ δευτέρῳ, 6:37 (in ᵐ5 6:4) ἐν μηνὶ Νεισῷ καὶ τῷ δευτέρῳ μηνί ᵐ5 Manuscripts ἐν μηνὶ Ζιου μηνὶ τῷ δευτέρῳ; ᵐ5L (only 6:37) ἐν δευτέρῳ μηνί, ἐν μηνὶ Ζιου; — (si vera lectio compare perhaps Aramaic זִיו brightness, freshness, so Biblical Aramaic Daniel 2:31 +; compare נִיצָנַיָּא זִיו יֶרַח ᵑ7 month of brightness of flowers; Assyrian zîmu (zîvu), DlPr 152 f. compare NöZMG 1886, 732; Thes and others derive זִיו זִו, ( = זְהִיו) from זהה in sense be bright, splendid, etc., compare Arabic increase, thrive (of seed-produce), a beautiful and bright, or fresh, plant; Aramaic זְהָא, adjective זָהוֺהָא haughty, proud; glory, boast, be magnificent; yet compare Ol§ 174 near the end)
זוּ זוֺ,.