Meanwhile the hard problem here seems to be related to English orthography?
Pretty sure Phil (RIP) correctly spelled the word "two" in his original rendering of this quote.
Many wits, and undoubtedly some twits have extended this to argue that there are TWO hard problems in CS: cache invalidation, naming things, and off-by-one errors!
(IYKYK)
https://www.karlton.org/
https://m.wikidata.org/wiki/Q99194342