Entry = Hesychius epsilon3681 and Lexica Segueriana 224.2 (with the exception that in these two previous sources the nu-moveable is present at the end of the headword: e)cekklhsi/asen).
The headword must be quoted from somewhere; probably, as Latte on Hesychius suggests, the Septuagint, where there are several instances (e.g. Leviticus 8.4).