Harry Potter enters the Wizarding World with his eyes wide open, taking in the wonder and 'magic' of it all, while steadily paying attention to everything around him. He starts to notice correlations between the names of people and places that are surprisingly telling about them as a person. As such Ron gets the acquaintance treatment, Draco gets avoided like the plague after Harry looks up what his name means, whilst Neville and Hermione, the two other first years Harry met, get a friendly approach after determining their names don't mean anything harmful or malicious. Harry explains the name thing to both Hermione and Neville after they become friends, and while skeptical, they can't help but see the patterns around them too.
Fast forward to third year. Harry's spent quite a bit of time paying attention to names, particularly those who might mean him harm, since he missed the bit with Lockhart and Quirrel. So he then meets Professor Remus Lupin. All three of this version of the Golden trio catch the significance immediately, and hoping to nip another Defense Professor out to kill him in the bud, the three confront him at wand point. He admits to being a werewolf, never having noticed the correlation between his name and his disease before.
At this point, Remus could be a 'new' name given upon his being bitten, and he might not remember his birth name, or it really could be a 'coincidence'. Either way, watch Harry as he continues to go through figuring things out based on the names of things, coming to conclusions that are both correct, and sometimes hilariously wrong. I mean, imagine how Harry with this philosophy would react to learning of a family with the name 'Lovegood'? Cue adolescent blushing and stammering whilst Luna looks on dreamily/innocently (or maybe not so innocently XD)