best bib and tucker
One's finest clothes, dressed up, as in The men were told to put on their best bib and tucker for the dinner dance. Although wearing either a bib (frill at front of a man's shirt) or a tucker (ornamental lace covering a woman's neck and shoulders) is obsolete, the phrase survives. [Mid-1700s] For a synonym, see Sunday best.
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.