"eat the evening meal," late 13c., from Old French super, which probably is from soupe "broth" (see soup), until recently still the traditional evening meal of French workers.
"sip," Old English supan (West Saxon), suppan, supian (Northumbrian) "to sip, swallow," from Proto-Germanic *supanan (cf. Old Norse supa "to sip, drink," Middle Low German supen, Dutch zuipen "to drink, tipple, booze," Old High German sufan, German saufen "to drink, booze"), from PIE *sub-, possibly an extended form of root *seue- (2) "to take liquid" (cf. Sanskrit sunoti "presses out juice," soma; Avestan haoma, Persian hom "juice;" Greek huetos "rain," huein "to rain;" Latin sugere "to suck," succus "juice, sap;" Lithuanian sula "flowing sap;" Old Church Slavonic soku "sap," susati "suck;" Middle Irish suth "sap;" Old English seaw "sap").