No reservations, restrictions, or excuses, as in You'd better be there tomorrow, and no ifs, ands, or buts about it. This expression uses the conjunctions to stand for the conditions and objections that they introduce. The earliest phrase to appear was ifs and ands in the 1600s. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.