Katakana history question

I have a question about the katakana that can not easily seem to be answered with a search engine.

Apparently the katakana started as a form of shorthand to help learn the kanji for Buddhist monks and the hiragana was invented by imperial court women. I can not seem to find much on the history, however, of when the katakana started being applied specifically for European loan words. Did this date from the time period that Japan was closed? Did date from when Japan was opened in modernizing? Did it not happen until after World War II? Or did it have some precedent in earlier Chinese translations also? What were the circumstances in which this started happening?

Maybe cookies are making my search engine clog with advertisements too much but I can not seem to find much information on the subject.

I am sure you have tried Wiki. The history is murky.
The linguist's long official stand is katakana was derived from Kanji. But a recent research casts it might come from Hebrew. Too many similarities.
Search for the Ten Lost Tribes & related articles on Google & YouTube.
What do you think?

I assume the OP is trying to figure out when and how "loan words" became to be written in katakana while other words are not.

A quick Google search on the key phrase 外来語はいつからカタカナ (since when are loan words in katakana) does help. By the way, apart from the loan word issue, katakana was more commonly used than hiragana until the end of WW2, and that katakana era, I think, lasted for quite a while, although for example in the Heian era, females were expected to use hiragana while males were expected to use kanbun.

http://www.google.co.jp/search?q=%E5%A4%96%E6%9D%A5%E8%AA%9E%E3%81%AF%...

ay: But a recent research casts it might come from Hebrew. Too many similarities.

One thing I can point out that katakana letters had variety of shapes.
Even in the one age in the history, there were different katakana shapes for a same syllable.
(It was only in 1900 that shapes of katakana letters were officially standardized.)
So, I suppose that similarities in shapes between Hebrew used at one moment and katakana used at one moment cannot perfectly support the Hebrew-origin theory.

Guest 7: when the katakana started being applied specifically for European loan words

Katakana and hiragana got established in Heian period, which lasted until the 12th century.
European words began to be directly taken into Japanese around the end of Muromachi period in the 16th century.
In the early ages, some might have been written with katakana, some with hiragana or some with kanji.
(By the way, there are some old European-origin loan words which are now usually written not with katakana.
e.g. " 天ぷら [tempura]")

If you are asking when writing European loan words with katakana became a common custom,
I answer that it was probably in Meiji Era (1868 - ).
(In the field of literature, mixture of kanji, hiragana and katakana seem to have got established as a style during Meiji Era.)
However, even in Meiji Era, katakana was not the only way to express European loan words.
Also kanji characters were used as phonograms for some words.
e.g. " 瓦斯 " for " ガス [gasu]" coming from "gas."

Uco: katakana was more commonly used than hiragana until the end of WW2, and that katakana era, I think, lasted for quite a while

Katakana was preferred to hiragana for laws and official documents written after around the beginning of Meiji Era until the end of WW2.
e.g.
: The so-called Meiji constitution was fully written with kanji and katakana; after the current Constitution, which was promulgated in 1946, is written with kanji and hiragana.
: Hiragana was installed into Civil Code and Criminal Code only in Heisei Era (1989 - ).
: Commercial Code has both a hiragana-installed part and a kanji-and-katakana part.

Guest 7: Apparently the katakana started as a form of shorthand to help learn the kanji for Buddhist monks

I guess that the main purpose was not to help learn kanji characters.

Kanji characters are originally ideograms.
However in Japanese before the emergence of katakana and hiragana, kanji characters were commonly used also as phonograms, mainly to express syllables.
(Such characters are called "万葉仮名 [Man'you-gana]" after 万葉集 [Man'you-shuu], the oldest existing anthology of Japanese poems.)

In Heian period, people such as Buddhist monks read some classical Chinese writings using Japanese; they had to note readings quickly.
This purpose is considered to boost application of katakana letters.

I replace
: "written after around the beginning of Meiji Era until the end of WW2."
by "written roughly between the beginning of Meiji Era and the end of WW2."
: "after the current Constitution,..."
by "the current Constitution..."

May I ask what credential you have, omotenashi?