Analog doesn't have to refer to anything digital, it's used in a variety of ways. The English language is adaptive and constantly changing. That is why new editions of dictionaries are printed. Quick FYI, Ain't is now a word, and it is in the dictionary. Gay used to mean happy. Literally no longer means literally. The list goes on, but I digress.
analog or analogue (ăn′ə-lôg′)
Noun
1. An organ or structure that is similar in function to one in another kind of organism but is of dissimilar evolutionary origin. The wings of birds and the wings of insects are analogs.
2. A chemical compound that has a similar structure and similar chemical properties to those of another compound, but differs from it by a single element or group. The antibiotic amoxicillin, for example, is an analog of penicillin, differing from the latter by the addition of an amino group.