You know how your computer underlines your misspelled words in red? If you use a word a lot but your dictionary doesn’t know the word, you can stop it from “correcting” you by adding the word to your dictionary by right-clickig it and choosing the “learn” or “add to dictionary” choice.  Your computer will keep a list of these words.
Since no two people will have the same list of words, this strikes me not so much as a fingerprint as it is a bit of personality – part of the computer’s soul; its unique, ongoing  logomachy.
If you have a mac, your list is here:  ~/Library/Spelling   Go check your list out!
I haven’t had my lovely Macbook Pro for very long, so I haven’t added many words to her custom dictionary. My list is short, yet revealing. When I look over my list, every word has meaning to me – some more special than others.
Here are the words I have told my computer to Learn so she stops correcting me:
cunt douchebag Drupal hisnameistimmy htaccess kerfluffle NationBuilder Ponzi Shotwell