*gre-no-
*gr?-no-, Proto-Indo-European root meaning "grain."
It forms all or part of: corn (n.1); filigree; garner; garnet; grain; granary; grange; granger; granite; granular; granule; grenade; grenadine; kernel; pomegranate. It is the hypothetical source of/evidence for its existence is provided by: Latin granum "seed," Old Church Slavonic zruno "grain," Lithuanian žirnis "pea," Old English corn.

Sources:

• A Dictionary of Selected Synonyms in the Principal Indo-European Languages, University of Chicago (By: Carl Darling Buck) 1988.
• Etymological Dictionary of Latin and the other Italic Languages (By: Michiel de Vaan) 2008.
• The American Heritage Dictionary of Indo-European Roots (By: Calvert Watkins) 2000.
• Noun Declension in Indo-European (Sindhueuropaia Deklination Nomnes) By: Carlos Quiles.
• Online Etymology Dictionary (By: Douglas Harper)