Per misadventure
Defined in 2 dictionaries — Ballentine's (1916), Black's (1910)
Ballentine's Law Dictionary
James A. Ballentine · 1916
By misfortune. Per mitter le droit. By the release of the right. See 19 N. Y. 384. Per mitter restate. By the release of the estate. See 19 N. Y. 384. Per my et per tout. By the half and by the whole. See 2 Bl. Comm. 182.
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
In old English law. By mischance. 4 Bl. Comm. 182. The same with per infortunium, (q. v.)