From garar (as in gerah); properly, (like gargar) a kernel (round as if scraped), i.e. A gerah or small weight (and coin) -- gerah.
see HEBREW garar
see HEBREW gerah
see HEBREW gargar
H1626. gerah
II. גֵּרָה noun feminine a weight, 20th part of shekel, gerah (Assyrian girû, ZehnpfBAS i. 506) — גֵּרָה Exodus 30:13 4t. — Only in definition of שֶׁקֶל, with number עֶשְׂרִים 30:13; Leviticus 27:25; Numbers 3:47; 18:16; Ezekiel 45:12.