Presumably a compound of durmast + oak, but the origin of durmast is unclear and possibly a result of scribal error. The first edition Oxford English Dictionary suggests that Thomas Martyn's dictionary for gardeners and botanists (1798) originated the word through misreading dun mast ("light-brown acorn").
- durmast, n. James A. H. Murray [et al.], editor (1884–1928) A New English Dictionary on Historical Principles (Oxford English Dictionary), London: Clarendon Press, OCLC 15566697; and The Oxford English Dictionary; being a Corrected Re-issue with an Introduction, Supplement, and Bibliography of A New English Dictionary on Historical Principles (the First Supplement), Oxford: Clarendon Press, 1933, OCLC 2748467.
- Thomas Martyn; Philip Miller (1798) A companion to the gardener's and botanists' dictionary ... By the late Philip Miller, F. and C. Rivington, OCLC 643825282