just for old time's sake (hi Jackie!), here's what the dictionaries have to say:
M-W gives it solely as deluxe.
AHD prefers deluxe, but lists de luxe as a variant.
OED Online: ||de luxe [Fr., lit. ‘of luxury’.]
Luxurious, sumptuous; of a superior kind.
1819 Edition de luxe [see LUXE 2]. 1865 ‘OUIDA’ Strathmore viii, I wonder
governments don't tax good talk; it's quite a luxury, and they might add de luxe. 1885
Edition de luxe [see LUXE 2]. 1890 Trains de luxe [see LUXE 2]. 1908 Westm. Gaz. 6
June 5/1 We are conscious of something De luxe, but not oppressed by the sense of it.
1934 Punch 20 June 679/3 They will disclose Britannia, enthroned on the top of a de
luxe model of one of those erections from which they mend tram-wires. 1949 E. POUND
Pisan Cantos lxxvii. 52 Before the deluxe car carried him over the precipice. 1955 T. H.
PEAR Eng. Social Differences viii. 182 Members of the upper economic strata..who
patronise hotels de luxe. 1970 K. CHESNEY Victorian Underworld 336 These places
were often little businesses engaged in a de luxe trade, glovers, bonnet makers, perfumers
and so on.
so perhaps we have Ezra Pound to thank for the concatenation? and using capitalization seems to be ostentatious in the extreme, along the same lines as dining at the American Grille.
