nLychnoscope(Arch) Same as Low side window, under Low, a.
Century Dictionary and Cyclopedia
nlychnoscopeIn architecture, a small opening like a window, usually placed in the south chancel-wall of a church, and lower than the other windows, for what purpose is not strictly known. Also called low side window. Gwilt. “This is generally a small window in a church under a larger one. … The term itself is (like hagioscope) only of this [19th] century, and may have been coined on the erroneous idea that the windows were constructed that lepers (or anchorets) might behold the altar lights. On the other hand, that idea may be correct. Another theory is that of a confessional.” N. and Q., 6th ser., IX. 289.
Chambers's Twentieth Century Dictionary
Lychnoscopea small window-like opening in the south wall of a church