Where did 'per' come from....

Looked in Wiktionary, which describes 'as per usual' as an adverb, meaning 'as usual'.
(Again, no mention of my Granny. I may have to add her myself!)

Just looked on Wiki but it did not mention anagram's Granny

Etymology 1
From Latin per (“through, during”), from Proto-Indo-European *per.
[edit]Preposition
per for each
Admission is £10 per person.
to each, in each (used in expressing ratios of units)
miles per gallon
beats per minute
(medicine) via (the), by (the), through (the) (followed by Latin name for an orifice)
Introduce the endoscope per nasum.
The medication is to be administered per os.
in accordance with
I parked my car at the curb per your request.
[edit]Usage notes
The preposition per is typically followed by a singular noun phrase with no determiner.
Take one pill per day. not Take one pill per a day.
It is sometimes followed by plural noun phrases, almost always determined by 100, 1,000, 100,00, etc.
The abortion rate in the U.S. has dropped since 1980 from nearly 30 per 1,000 women of childbearing age, to less than 20.

Maybe it was your Granny who started it Anagram? I think I may have started one recently when I referred to my DH's 'rellies' coming for the day. Now everyone else seems to be using it when referring to relatives.

Well, if she did, fashion-speak is older than we thought!

Ah Anagram Granny may not have seemed fashionable to you but she may that felt she was, just like some of us!

My granny used to say "as per usual" very often. That was over 50 years ago and she wasn't fashionable at all!

per means according to doesn't it?

As in: "as per my letter of the 25th May"

I've actually heard as per usual so much that it's becoming shortened to "as per".

As in: "He's forgotten to pick his dirty laundry off the floor, as per"

Is it from 'per pro' meaning on behalf of?

Until you find yourself using it and going

Don't know, but I've used it too .

I think it's one of those fashion-speak things that one can pick up without noticing.