Bible Dictionary · G
Gerah
A bean, probably of the carob tree, the smallest weight, and also the smallest piece of money, among the Hebrews, equal to the twentieth part of a shekel (Ex 30:13; Lev 27:25; Num 3:47). This word came into use in the same way as our word “grain,” from a grain of wheat.
From Easton’s Bible Dictionary (1897), by Matthew George Easton.