early 14c., "a quarrel, dispute, disagreement" (now archaic), from Old French debat, from debatre(see debate (v.)). Sense of "contention by argument" is from late 14c., that of "a formal dispute, a debating contest, interchange of arguments in a somewhat formal manner" is perhaps from early 15c.
"international organization of the Communist Party," founded 1919, from contraction of Communist International and modeled on Russian Komintern.
formal term of address to a lady, 1590s, see madam, which is an earlier borrowing of the same French phrase. Originally a title of respect for a woman of rank, now given to any married woman. It is more formal or affected than madam. OED recommends madam as an English title, madame in reference to foreign women.