Many names in the Old Testament are transliterated and used today. The names from later books -- such as Jonathan (Yonatan), Samuel (Shemu'el), and Joshua (Yehoshu'a) -- all seem to follow basic rules like having a j instead of the Hebrew "yud" and a ch or h for the harsher sounds. However, names from the beginning of Genesis -- Eve (Chavah), Abel (Hevel), Enoch (Chanokh), and others -- sound quite different from their Hebrew originals. Why do these names seem to be transliterated differently compared to later names?
The loss of the initial heth in Eve, Abel and Enoch (as well as Anna and other names) is due to their journey via Koine Greek, which represented the word-initial aspiration of heth (and he) with a 'rough breathing' diacritic on the initial vowel. Since the breathing marks weren't used regularly, and since the [h] sound was eventually dropped in pronunciation, the names entered Latin and English with no aspiration sound.
It's also important to remember that both the English pronunciation and Modern Hebrew pronunciation have changed significantly since the names were formed. The v in the Latin Eva and ו in חַוָּה were both pronounced w. The intervocalic β in the Greek Ἄβελ (Abel) was closer to a v than word-initial βs were. And Biblical Hebrew had more vowels than Modern Hebrew does (which might partly explain why it's Eva rather than Ava, or Abel rather than Ebel).