Lewis Short
thēca (noun F) = θήκη,:
* That in which any thing is enclosed, an envelope, hull, cover, case, sheath, etc. (syn. vagina): grani,Varr. R. R. 1, 48, 1: efferri sine thecis vasa,Cic. Verr. 2, 4, 23, § 52; id. Att. 4, 7, 2; Quint. 6, 3, 61: calamaria,Suet. Claud. 35; Mart. 14, 19, 1; Amm. 28, 4, 13.
Charlton T. Lewis, Charles Short, A Latin Dictionary