From an unused root meaning to be sour; an immature grape -- unripe grape.
Englishman's Concordance
1) unripe or sour grapes Part of Speech: noun masculine collective A Related Word by BDB/Strong’s Number: from an unused root meaning to be sour Same Word by TWOT Number: 257
Job 15:33 HEB:יַחְמֹ֣ס כַּגֶּ֣פֶן בִּסְר֑וֹ וְיַשְׁלֵ֥ךְ כַּ֝זַּ֗יִת KJV: He shall shake off his unripe grape as the vine, INT: will drop the vine grape and will cast the olive
