But, Lighter, as Mad Dogs & Englishmen [1931{NY}/32{London}] is about exactly contemporary with your terminus a quo date for E Nell, your putative 'coincidence' would appear either unlikely or suggestive of same-authorship. Your dates make my point feel even stronger to me. Coward had bored/boring caribous much in mind & they would out! &, as you yourself point out, it is much more probably of CisAtlantic than TransAtlantic origin.

~M~

BTW,in what dialect does 'milieu' rhyme with 'caribou'?