after meat, mustard Too late; no longer of any use. The original expression was the French c’est de la moutarde après dîner, which first appeared in English as ’like mustard after dinner’ (John Adams, Adams- Warren Correspondence, 1807), before evolving into the more common after meat, mustard. This phrase expresses the uselessness of offering something after the need for it has already passed, as does the similar Latin expression post bellum, auxilium ‘after the war, aid.’
third wheel An extra, unnecessary, or unwanted person, especially one whose presence serves no useful purpose; a person who interferes with or prevents the successful completion of a project, task, or other matter. The concept is undoubtedly similar to the sentiments expressed in the familiar adage, “Two’s company, but three’s a crowd.” Although the derivation of this expression is not certain, it probably alludes to the uselessness of a third wheel on a vehicle which normally has two. Today one frequently hears fifth wheel, most probably because most vehicles now have four.