Bundestag (n.)

German federal council, 1879, from German Bundestag, from genitive of Bund "league, confederacy, association" (related to English band (n.2) and bind (v.)) + tag, literally "day;" as a verb, tagen, "to sit in conference" (see day; also compare adjourn). Hence also Bundesrat "federal council of the German empire" (1872), from rat, rath "council" (see rathskeller).