a Hebrew word, meaning a grain or kernel, and hence a small weight; the smallest weight

It was a bean, probably of the carob tree.

This was the smallest weight and also the smallest piece of money among the Hebrews, equal to the twentieth part of a shekel (Exodus 30:13; Leviticus 27:25; Numbers 3:47). It was the twentieth part of a shekel, and equal to 12 grains.

This word came into use in the same way as our word “grain,” from a grain of wheat.