means the deliberate supply of water to crops or land through channels, pipes, or sprinklers to help plants grow where rainfall won't do the job alone

from from Latin 'irrigare,' to water or moisten — built from 'in-' (into) plus 'rigare' (to wet, to lead water). The same 'rigare' likely waters the word 'rain'-adjacent ideas across Indo-European, though the cousins are debated. It entered English in the early modern period, first as a medical term for washing a wound, then spreading outward to the fields where it now mostly lives.