Strong's Definition
probably patrial from an unused noun meaning slenderness; a Mithnite, or inhabitant of Methen
KJV Usage: Mithnite
STEPBible — Tyndale Abridged Hebrew Lexicon
מִתְנִי (mit.ni) — Mithnite. Someone descended from Mithn(?), only mentioned at 1Ch.11.43 § Mithnite = "athlete" 1) unknown derivation 1a) used in description of Joshaphat, one of David's guards
UBS Dictionary of Biblical Hebrew
adj
UBS Dictionary of Biblical Hebrew © United Bible Societies, licensed CC BY-SA 4.0.
Brown-Driver-Briggs Hebrew Lexicon
מִתְנִי adj.gent. (deriv. unknown);—only 1 Ch 11:43. ref