'Strange' predates the quark/parton model, and was a placeholder name for a particular unexplained phenomenon; similar to how the prefix 'dark' gets used. In p

'Strange' predates the quark/parton model, and was a placeholder name for a particular unexplained phenomenon; similar to how the prefix 'dark' gets used. In particular, collider experiments were giving rise to a 'particle zoo' of pions, kaons, lambdas, etc. all of which were assumed to be fundamental. Some of these lasted much longer than expected, and were called "strange". It turned out that these could be modelled by giving fundamental particles a new property, which got the name "strangeness". Similar to how particles can have "charge", which is zero for neutral particles; non-strange particles have zero strangeness. Their long lifetime was explained due to the strong force conserving strangeness: collisions between non-strange particles can make pairs of particles with positive/negative strangeness (as long as it sums to zero); but once those individual particles have separated they can no longer decay via the strong force; they have to wait for the weak force, which gives them a longer half-life. It was only later, once the quark model became more accepted, that these particles were no longer considered fundamental, and "strangeness" could be explained as "containing strange quarks". On the other hand charm, beauty/bottom and truth/top seem to all be built on the quark model from the start; which makes the whimsy in their names more deliberate. --- FYI the BBC's Horizon did an episode in the 60s called "Strangeness Minus Three" ( https://www.bbc.co.uk/programmes/p01z4p1j https://www.bbc.co.uk/programmes/p01z4p1j ) which is interesting to watch in hindsight, now that we have quarks and the standard model; and makes a nice comparison to the more recent search for the Higgs boson. --- Tangentially this idea, of a new property whose conservation prevents massive particles from decaying, also arises in supersymmetric models of dark matter. There, supersymmetric particles have a different "R parity" to normal particles, which prevents them decaying even if they're very massive; such particles are a candidate for dark matter.