Abarim Publications' online Biblical Hebrew Dictionary
There are two separate roots with the form רסס (rasas), but their meanings are so much adjacent that one may wonder whether a Hebrew audience actually realized that there were two separate roots involved:
The root-verb רסס (rasas I) means to moisten. It's related to a similar Arabic verb that means to sprinkle. Our Hebrew verb occurs only once, in Ezekiel 46:14.
The sole Biblical derivative of our verb is the masculine noun רסיס (rasis), meaning drop (of dew). This noun also occurs only once, in the Song of Solomon 5:2.
The assumed root רסס (rss II) isn't used in verb in the Bible and only one derivative remains: the masculine noun תירס (rasis), meaning fragment. Note that this noun is identical to the previous one and not all that far removed in meaning. The latter noun may have helped to form the modern Hebrew word for maize. In the Bible it occurs only once, in Amos 6:11.