Amor proprio, motu propio

I know, I know. It is amor propio; not amor proprio. But what about motu propio? I dealt with this in passing here.

My professor in Civil Law review, former RTC Judge Mein Paredes, uses motu propio. Other authors, professors, and lecturers use motu proprio.

Still I think I need to get deeper into this motu propio/proprio thing because when I read the masterful dissent of Justice Leonen on the bail granted by the SC for Enrile there was, lo and behold, motu propio sticking out like a sore thumb.

If you are looking for a definitive discussion of the right to bail as enshrined in the constitution and fleshed out by Rule 114 Justice Leonen's is the go-to exposition. Get it here.

For the moment, though, we are interested in this section:

Amor propio is spanish. So it is not hard to find its meaning through online dictionaries like in this one.   It means a feeling of self-worth. There is no such phrase as amor proprio in Spanish.

Motu propio appears in US Legal in this entry:

Motu propio is a Latin term meaning "on his own impulse". It is used to refer to a document that is issued and personally signed by the Pope. It may be contain instructional matter, administrative matters of church law or governing bodies, or used to grant a special favor.

Other dictionaries use motu proprio as in this from the online version of Black's Law Dictionary:

What is MOTU PROPRIO?
Lat. Of his own motion. The commencing words of a certain kind of papal rescript

So which is which? See here for a discussion for motu propio vs motu proprio.

Personally I go for motu proprio as found in this entry of wikipedia.