You've got her in your pocket
And there's no way out now
Put it in the safe and lock it
'Cause it's home sweet home
What I noticed is that the third line - while it sounds the same when sung - could be written as "Put it in the safe and lock it" or "Put it in the safe and locket." Each rendering has its advantages.
"Safe and locket" implies extra security. The singer/speaker advises "you" to "put it" in two different locations, almost so that an extra back-up copy is available. Additionally, a locket is kept closer and is more personal than a pocket.
This might be looking at it too closely, but "safe and lock it" could represent a higher level of security via the mosaic rhyme between "pocket" and "lock it." There's an extra level of complexity, like a lock that's more impervious to being picked.