The 'Go Back' rollover tooltip text you refer to (which is displayed only when the user hovers over the Back Button) can be changed via the languageList configuration option.
More details on the languageList option can be found here.
This configuration option is not found in JuiceboxBuilder-Pro but you can add it to a gallery by opening the 'config.xml' file in a plain text editor and adding the option as an attribute to the opening <juiceboxgallery> tag.
To change the 'Go Back' text to 'Home', use the following:
languageList="Show Thumbnails|Hide Thumbnails|Expand Gallery|Close Gallery|Open Image in New Window|Images|Next Image|Previous Image|Play Audio|Pause Audio|Show Information|Hide Information|Start AutoPlay|Stop AutoPlay|AutoPlay ON|AutoPlay OFF|Home|Buy this Image|Share on Facebook|Share on Twitter|Share on Google+|Share on Pinterest|Share on Tumblr|of"
The opening <juiceboxgallery> tag in your 'config.xml' file might look something like this:
<juiceboxgallery
galleryTitle="Juicebox-Pro Gallery"
languageList="Show Thumbnails|Hide Thumbnails|Expand Gallery|Close Gallery|Open Image in New Window|Images|Next Image|Previous Image|Play Audio|Pause Audio|Show Information|Hide Information|Start AutoPlay|Stop AutoPlay|AutoPlay ON|AutoPlay OFF|Home|Buy this Image|Share on Facebook|Share on Twitter|Share on Google+|Share on Pinterest|Share on Tumblr|of"
>