apropos of

Regarding; with respect to; referring to. From the French à propos, meaning "to purpose." Apropos of the decision reached at this morning's board meeting, I think we should move ahead with the staff reduction directly. And then he just punched Jeremy in the face, apropos of nothing!

Concerning, in connection with, as in Apropos of keeping in touch, I haven't heard from her in months. This idiom was a borrowing of the French à propos de ("to the purpose of") in the 17th century. At first it was used without of and meant "fitting" or "opportune," as in Their prompt arrival was very appropos. By the 1700s it was also being used with of, as in the current idiom, for "concerning" or "by way of."