And each cross of silver a shield will be. As we will, so mote it be.[from Morrigan's Cross]
The silliness of rhyming spells was bad enough; but "mote", I thought, was not an auxilliary verb, and I couldn't find it in the Concise Oxford either.
You have to be careful, though, before you castigate a favourite, so I looked for "mote" on the web and lo!
I see now that it's also in my 1955 edition of the Shorter Oxford Dictionary. ("Shorter", by the way, does not mean short: the SOD contains over two and a half thousand large format pages and weighs eight pounds.)