It's definitely intriguing how the meanings of words can change over the years. A Blog Around the Clock recently presented a quote that claimed that Charles II described the newly-built St Paul's Cathedral as "awful, pompous and artificial". This was entirely complimentary - "awful" indicates something that inspires awe, "pompous" roughly means "majestic", while "artificial" means that it indicated a great deal of artifice on the part of its builder - and "artifice" would have meant "technical or artistic skill", having not yet gained its current connotation of duplicity and deception. "Automaton" is another word that has changed significantly in meaning. It literally means "self-moving", and so when it was first coined would have indicated the independent, undirected movement and action of the subject - almost the complete opposite of its current usage.
I bring up those examples to segue into another change in meaning that I came across yesterday. I happen to have in front of me a copy of the Proceedings of the Zoological Society of London for 1866, in which (amongst other things) W. Lilljeborg presented a revised classification for birds. In explaining the principles on which he based his classification, Professor Lilljeborg notes:
Irritability seems to us to be the most distinguishing character for birds, and this should consequently be taken into consideration more than others with regard to their classification.
I'm sorry? You're classifying birds according to how irritable they are? Fortunately, Lilljeborg further explains, "We do not by irritability mean the muscular strength alone, but vivacity and activity generally". Lilljeborg was basing his classification on a principle that evolution had proceeded from less derived, more sluggish forms to more derived and accomplished forms. All horribly Scala Naturae-based, of course, and more than a little inaccurate in some regards:
The swimmers seem to us the lowest, from their showing a tendency to the lowest form of vertebrated animals - the fish-form. In the [penguins], where the wings resemble fins, and where they, as in all other diving birds, serve as such, we have this form most strongly designated. The heavy, clumsy structure, with small wings and short legs, also makes them generally less active than other birds, and shows a lower development of the type of bird.
A description obviously heavily biased by observations of penguins almost solely on land, not in the water where they are far more adept. I also had to snicker somewhat at Lilljeborg's complaint about the previous tradition of placing the birds of prey (rather than the passerines he favoured) at the "summit" of avian evolution:
A system that places the dirty vultures highest, does not seem to us to indicate a correct idea of the nature of birds.
Lest I give you too negative impression of Lilljeborg's skills as a systematist, his final classification stands up fairly well by the standards of the time. The classification itself was generally based on good anatomy - the philosophical considerations mostly affected what order he listed things in. Still, I couldn't read that section on "irritability" without getting the mental image of Professor Lilljeborg, his fingers heavily bandaged, making his way down a row of birds sitting in cages, poking each one in turn with a chopstick and seeing how long it took to snap back. One suspects he probably left the eagle until last.
Lilljeborg, W. 1866. Outlines of a systematic review of the class of birds. Proceedings of the Zoological Society of London 1866: 5-20.