Why is "boyfriend" transliterated as 「ボーイフレンド 」 instead of 「ボイフレンド」?


Most of the time, I can guess correctly how to write an english
[Gairaigo](https://en.wikipedia.org/wiki/Gairaigo) word in katakana. When I am
mistaken, I understand the correct writing and learn from it. Some feel a bit
odd, but with time I get used to it. I find it very interesting how the
english sounds are twisted to fit in the japanese style.

But this one got me puzzled. For the word "boyfriend", the transliteration of
choice is **ボーイフレンド** , which feels _very_ awkward for me. I was expecting
**ボイフレンド** instead, but that gets only 34 thousand hits on Google Japanese,
while the former has about 8 million hits.

As a comparison, I am fine with the long vowels in the following examples:

  * Girl: ガール
  * Answer: アンサー
  * Ball: ボール
  * Party: パーティー
  * Elevator: エレベーター

**My question is, is it just my intuition that is wrong, or is there something
else behind this? Maybe some sort of linguistic phenomenon such
as[Metathesis](https://en.wikipedia.org/wiki/Metathesis_\(linguistics\)) or
[Malapropism](https://en.wikipedia.org/wiki/Malapropism)? Maybe someone
misspelled it at the first time and people ended up using it anyway?**

If it is just my intuition that is wrong, that would totally be a valid
answer, although quite embarassing... I am expecting something else for this
specific word because it seems weirder than usual. By the way, English is not
my first language (nor Japanese, of course).




There are not strict correspondences of phoneme between the original English
words and Katakana in Japanese.  

You can often see these examples as below.  
- joy -> ジョイ (not *ジョーイ)  
- toy -> トイ (not *トーイ)  
  
So it is no wonder you think _boy_ is written as ボイ.  

However, ボイ appears much less than ボーイ.  
That is because ボーイ is recognized as just a Japanese word.  




There are not strict correspondences of phoneme between the original English
words and Katakana in Japanese.  

You can often see these examples as below.  
- joy -> ジョイ (not *ジョーイ)  
- toy -> トイ (not *トーイ)  
  
So it is no wonder you think _boy_ is written as ボイ.  

However, ボイ appears much less than ボーイ.  
That is because ボーイ is recognized as just a Japanese word.  

