The only free and comprehensive online etymological dictionary of the Spanish language
banco (Noun) (finance) "bank"
13th cent. From French banque 'id.,' from Italian banca "moneychanger's table," from Old Italian banca "bench." From a West Germanic language, probably Lombardic *bank (compare Old Saxon bank "bench," Old High German banc 'id.'). From Proto-Germanic *banki- 'id.' Of unknown origin. Possibly a substrate word.
Indo-European
Romance
Asturian bancu, Portuguese banco, Galician banco, Catalan banc, French banque, Romanian banca
Germanic
Old Norse bekkr, Old High German banc, English bench