Plagal

plagal \ˈplā-gəl\ adjective: 1. of a church mode, having the keynote on the fourth scale step, 2. of a cadence, progressing from the subdominant chord to the tonic

Etymology: Medieval Latin plagalis, ultimately from Greek plagios oblique, sideways, from plagos side; akin to Latin plaga net, region, Greek pelagos sea

Plagal’s etymology is related to yesterday’s word pelagic.