Like a lot of Google products, Photos has a lot of forebears. Picasa was one of them, as was Google+ (IIRC, the Picasa team was folded into Google+ when Larry refocused the company on Social in 2011). Sounds like Bump was also aquihired into it, and I think there was also a lot of cross-pollination between Image Search, Research, and Google Photos around some of the search & content recognition features.