Procuration (from Latin procurare 'to take care of') is the action of taking care of, hence management, stewardship, agency. The word is applied to the authority or power delegated to a procurator, or agent, as well as to the exercise of such authority expressed frequently by procuration (per procurationem), or shortly per pro., or simply p.p.

The correct usage is the subject of some debate. It has been understood as both "through the agency of" and "on behalf of".

The reason for this is that the meaning of the phrase per procurationem is ambiguous if used with undeclinable English names.

Procuratio is related to the words "pro" (for/on behalf of/instead of) and "cura" (care/attention). It is thus close in meaning to "agency" — acting instead of someone. The phrase 'per procurationem' thus means "by/through agency".

Note that the phrase does not contain a preposition "of". This is because this idea would be expressed through the genitive case in Latin. With time, Latin or Latinized names fell out of usage, and the genitive case of the agent's name (in English "of Mr X") was thus lost. The original would look like this:

or

This seems to be the most simple and logical reading.

The other option is that "per procurationem" could be understood as a complete adverbial phrase in itself — "by the agency [of another]", without a dependent genitive. However, this would mean that two people signed the letter, one in his own person, one "by the agency of another" (without that other being expressly indicated).