사

Too mixed to pin down

A few lines here do contain the old humble -사- buried inside a verb: 믿사옵나이다 'we humbly believe', 찾아왔사와요, and 하느님이 보우하사 from the national anthem. But the rest are unrelated — 메찾사 is a show segment's acronym, 사 also means 'buy' (뭐 그렇게 어려운 거 사?). The archaic piece is real but these examples are too scattered to describe how it is used.

The examples below did not fully pin this one down — read them before relying on the entry above.