ὀπισθό-δομος · opistho-domos — LSJ
back chamber, inner cell of the old temple of Athena in the Acropolis at Athens, used as the Treasury, IG 1(2).139.17, al., Ar. Pl. 1193, D. 13.14, 24.136, IG 2(2).1388.73, etc. ; Delph. ὀπισσόδομος SIG 246 iii 35 (iv B. C.).
as Adj., at the back of a building, αἱ ὀ. στῆλαι Plb. 12.11.2.