I learned this word from family genealogy. There is still on record in MA State Archives lib. 129 folio 10 The Deposition of Jonas Humphrey...and Robert Randall.....(that) Ephraim Hunt(was) the reputed eldest son of Enoch Hunt...20 July 1688"
"And further the deponents say not"
So Ephraim was able to claim his inheritance.

I've used, and heard used, deposition, depose, deposed, etc. ....but I've never seen or heard or seen "depone". This must be uniquely USn, though true it is that UK/Oz/Zild don't have depositions in their legal systems... jj