In our language (Ukraine) - it translated as 7 lives, pound as I know is a unit of weight or monetary unit, how is it related? Does it have anything similar to life? Or it is just a translation of our country?
This is apparently alluding to Shakespeares "Merchant of Venice", were a debtor owes a pound of flesh - and since the protagonist in the movie is "paying back" seven lives, it's seven pounds.
According to Wikipedia, Will Smith confirmed the connection:
Will Smith is reported to have confirmed that the title refers to Shakespeare's The Merchant of Venice, in which a debtor must pay a pound of flesh
While, being a Shakespeare fan, that was basically the first thing I thought of, I don't think it makes a lot of sense, since nothing in the circumstances of the debt in the play is even remotely parallel to what happens in the movie. But if the main actor/producer confirms it, then that's probably it.