Do, Lego
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
Lat I give, I bequeath; or I give and bequeath. The formal words of making a bequest or legacy, in the Roman law. Titio et Seio hominem Stichum do, lego, I give and bequeath to Titius and Seius my man Stichus.
Inst 2, 20, 8, 30, 31.
The expression is literally retained in modern wills.