The noun is derived from Late Middle English rim (“cleft, crack, fissure”), from Latin rīma (“chink, cleft, crack, fissure”), ultimately from Proto-Indo-European *(H)reyH- (“to cut; to tear”). Doublet of rima. The verb is derived from Latin rīmārī, the present active infinitive of rīmor (“to explore; to probe; to search”), from rīma (see above) + -or.