It's not clear that this oft-repeated story of the origin of Alonzo Church's lambda notation is true. See https://en.wikipedia.org/wiki/Lambda_calculus#Origin_of_the_... for other instances where Alonzo Church has suggested it was more of an arbitrary choice of Greek letter.
Excellent, thank you for the link! Another commenter and I above have at greater length come to similar conclusions as in this Wikipedia subsection. I'll be more careful throwing this quote from Norvig around in future, the matter does seem uncertain.
In the short video from Scott dicussing it (https://inv.nadeko.net/watch?v=juXwu0Nqc3I) he says clearly that Church never discussed the lambda calculus while he was at Princeton, and that he thought Church was bitterly disappointed that his system was proven to be in some way inconsistent.
I wonder if Church named it after the Russell and Whitehead notation, and later wanted to distance himself from the whole thing so dismissed the notion. I had a quick look for the "unpublished letter to Harald Dickson" mentioned in the wikipedia there and can't find anything. Hmm.
