The word "malum, mali" has two principle meanings:
1) evil, bad
2) apple, fruit, apple tree
Does the association of 'malum' with evil have anything to do with the role of the apple in the story of Adam and Eve? If so, which was the original meaning of the word in pre-Chrsitian times? Did it mean 'apple' or 'evil'?
Or is it simply a coincidence that the word has these two meanings?
They're actually two words: "malum" (with no long vowel) meaning "evil" and "mālum" (with a long "a") meaning "apple".
The Romans probably had little to no contact with the Hebrews when the words "malum" and "mālum" were formed -- the words certainly predate the birth of Christ (and therefore Christianity), and Judaism wasn't exactly popular in Rome. (Judaism did exist in ancient Rome, but perhaps not back when the Romans first started to write, since there's no direct influence of the Hebrew script in Latin writing. I would think that the Romans would have started writing sooner in a Hebrew-based script if Jews were already there.)
However, it's possible that it did play a role in associating the fruit of the tree with apples specifically. The actual story only refers to it as "fruit". (I like to jokingly propose that it was actually a kumquat.) But the Vulgate Bible does describe the "lignum scientiae boni et mali", in which case a pun on "apple" does seem apparent, even though it was just an amusing accident of translation.
"Malum" is one of those words that is always waiting to trick you, considering that "malus, -i" means the mast of a ship. So technically "malum" could be three completely different things...
Horae quidem cedunt et dies et menses et anni, nec praeteritum tempus umquam revertitur nec quid sequatur sciri potest. Quod cuique temporis ad vivendum datur, eo debet esse contentus. --Cicero, De Senectute