From the same as metsach; a shin-piece of armor (as prominent), only plural -- greaves.
see HEBREW metsach
H4697. mitschah
[מִצְחָה] noun feminine greave(s); — only singular construct עַלדַֿגְלָיו נְחשֶׁת וּמִצְחַת 1 Samuel 17:6 and greaves of bronze upon his legs; < מִצְחֹת Vrss Th We Klo Dr Bu.
[מְצִלָּה], מְצִלִתָּיִם see I. צלל.
מְצֻלָה see צול. מִצְנֶ֫פֶת see צנף. p. 846f, 857
[מַצָּע] see יצע. [מִצְעָד] see צעד
מִצְעָר see צער
I, II. מִצְמָּה מִצְמֶּה, see צפה.
[מַצְמּוּנִים] see צפן