I don't know about Arabic, but in English 'Ann' is a name (more commonly spelled 'Anne').
If you take away an 'n', 'an' is used instead of 'a' for the indefinite article when it would be hard to pronounce the following word with an 'a' (ie. when the next word starts with a vowel sound). For example, 'a elephant' is hard to say and the 'a' is hard to hear, so an 'n' is added.