Apparently from shem and yada'; name of knowing; Shemida, an Israelite -- Shemida, Shemidah.
see HEBREW shem
see HEBREW yada'
H8061. Shemida
שְׁמִידָ֑ע proper name, masculine in Manasseh (the name knoweth? compare Sabean ירעסמהו DHMZMG xxxvii (1883), 16); — Numbers 26:22 (συμαερ), Joshua 17:2; 1 Chronicles 7:19, συμαρειμ, etc.; ᵐ5L σαμ(ε)ιδα(ε).