Several hypotheses have been proposed: * From со́пам се (sópam se, “to snap”) + -ол (-ol); * From Proto-Indo-European *sap- (“mucus”), whence Latin sapa (“wine must”); * From the root of си́пвам (sípvam, “to pour”), сип (sip, “embankment”), пря́спа (prjáspa, “snow drift”) (per Mladenov).