It seems both muhajaba (or muhajiba) and hijabi refer to women who observe hijab. Personally, I like hijabi because it sounds cute, and not for any serious reason.
Question: What is the difference between "muhajaba" and "hijabi"?
I'm guessing this would be best answered by someone who can speak Arabic.
Googling revealed a blog post Stories of a Hijab, although it's more rant than anything else.
The Arabic word which seems the common basis for all of these words is hijab (al-hijab الحجاب).
hijabi in first place doesn't sound Arabic unless it is meant as
"my hijab"
حِجَابِي
but in that case it should be pronounced like hijaabee with a prolonged "a" ا (alif الف) in the middle and "e" (sound of the kasra بِي diacritic which is taken from the letter ba' باء to the letter ya' ياء) at the end. If it is used as an adjective like:
حِجَابٍ المَرْأَة
hijab-u l-mar'ah (the scarf of a/the woman)
Then the use is rather wrong in the fasih (standard) language, however in some Arabic slangs or dialects people may call a girl hijabiyah حِجَابِيَّة (instead of muhajjabah or muhtajibah) which may include both mockery or a respectful attitude depending on the context and dialect, however the first could be the major case.
The most correct Arabic word describing a women wearing hijab is:
muhajjaba(h) مُحَجَّبَة is also used to describe a veiled woman (wearing hijab or hidden behind a hijab/veil).
muhajjiba(h) مُحَجَّبَة would mean the one who puts a veil/barrier between her and others!
There's also the word muhtajaba(h) مُحْتَجَبَة which i would tend to understand as a rather timid woman who hides her self because of fear.
My feeling is that where "hijabi" and "jihadi" are used to refer to a person who wears hijab or participates in jihad, the word has come from South Asian Muslim usage. In Arabic, as has been pointed out, the suffix -i can be possessive (my hijab, my jihad) or in some cases adjectival. An Arab refers to people who do things using the mu- prefix, so a person who undertakes jihad is a mujahid and a woman who wears hijab is a muhajaba (the -a is a feminine ending).
