Per and Cui
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
When a writ of entry ls brought against a second alienee or descendant from the disseisor, it is said to be in the per and cui, because the form of the writ is that the tenant had not entry but by and under a prior alienee, to whom the intruder himself demised it.
3 Bl. Comm. 181.