Vigor
Defined in 2 dictionaries — Black's (1910), Anderson (1889)
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
Lat. Strength; virtue; force; efficiency. Proprio vigore, by its own force.
A Dictionary of Law
William C. Anderson · 1889
Strength, efficacy, force. Ex proprio vigore. By its own inherent force. Ex vigore termini. By the strength of the word. Ex vigore terminorum. From, the very meaning of the language.