From kathash; a mortar; by analogy, a socket (of a tooth) -- hollow place, mortar.
see HEBREW kathash
H4388. maktesh
מַכְתֵּשׁ noun masculine mortar (place of pounding, braying; compare Palmyrene proper name, masculine מכתש = contundens VogNo. 97) — absolute ׳מ Proverbs 27:22 (see foregoing); hollow resembling a mortar Judges 15:19 (whence came forth a water-spring; compare GFM), Zephaniah 1:11 +? Jerusalem, compare SchwZAW x. (1890), 173 f.