Origin of this name is unclear, but a good guess is that it is an anagram of the original name for this genus Scepsis!
These moths were originally classified in genus
Scepsis. Thus "scape moth"? Himmelman, in
MIACY says that "scape" refers to the long basal joint of the antenna.
Die.net Dictionary says: Scape, n. [L. scapus shaft, stem, stalk; cf. Gr. ? a staff: cf. F. scape. Cf. Scepter.] 1. (Bot.) A peduncle rising from the ground or from a subterranean stem, as in the stemless violets, the bloodroot, and the like. 2. (Zool.) The long basal joint of the antenn[ae] of an insect. 3. (Arch.) (a) The shaft of a column. (b) The apophyge of a shaft.