Now this is what the Oxford Dictionary of English Surnames has got:
Darcey,
Darcy, D'Arcy:
Norman de Adreci, de Areci 1086;
William "Daresci" 1166;
Roger Arsi 1173-82;
Thomas Darcy 1276. From Arcy (La Manche [= the Channel]). The Irish
Darcy derives from
JOhn D'Arcy (14th) but is also an anglicizing of Ó Dorchaidhe "descendant of the dark man".
The Oxford Dictionary of First Names adds:
It has always retained a somewhat aristocratic flavour, which has enhanced its popularity as a given name. It is the surname of the
Hero of
Jane Austen's novel "Pride and Prejudice" (1813).
Hope this helps at least a bit.
Andy ;—)