From shamar in the original sense of pricking; a thorn; also (from its keenness for scratching) a gem, probably the diamond -- adamant (stone), brier, diamond.
see HEBREW shamar
H8068. shamir
I. שָׁמִיר noun masculine: Ezekiel 3:9 thorn(s), adamant, flint; — absolute ׳שׁ Isaiah 5:6 +; suffix שְׁמִירוֺ 10:17; —
1 collective thorns, thorn-bushes, token of waste-land, only Isaiah, + שַׁיִת Isaiah 5:6; 7:23-24, 25; 27:4; figurative 9:17; 10:17; שׁ ׳קוֺץ 32:13.
2 adamant, as sharp, ׳שׁ בְּצִמֹּרֶן ֗֗֗ כְּתוּבָה Jeremiah 17:1 ("" בַּדְוֶל בְּעֵט); as hard, figurative of prophet's firmness Ezekiel 3:9; Zechariah 7:12 figurative of hard heart.