Abracadabra, this magic trick is now a matter of language
Someone recently brought to our attention an article that talked about the famous magic trick where the magician saws his assistant in half. The question of how the trick is performed caught our attention – that is, until a beautiful, shiny linguistic question magically appeared.
What caught our attention was the question of how to talk about the trick later. Would you say the magician’s assistant was “sawn” in half, or were they “sawn” in half? Although we hope neither is true, either is acceptable.
The verb “saw” goes back to the noun “saw”. This is what linguists would call a “functional change”, which is when a word changes part of speech. There are many such changes in English, including “the drink/to drink”, “the tower/to tower over”, “the switch/to switch”, etc.
By the 13e century, “saw” had made its transition from noun to verb. It is a regular verb, so the past tense is “saw” and the past participle is “a sawed”.
In the 15e century, speakers began to create an irregular “saw” shape for the past tense and the past participle. Irregular verbs involve a change of vowel, for example, “to draw” in the past tense is “to draw”.
This is what happened to “seen”. The past tense changed vowel and became something like “soo”. The past participle became “sawn”, in the same way that the past participle of “draw” is “drawn”.
The irregular past tense of “seen” has died out, but the past participle “sawed” has remained. It is more popular in British English, while American English tends to prefer the regular form “sawn”.