Someone didn't know the word 'Messiah'

[Grumpyoldpersonwithcats]

Went to the bank yesterday while I was wearing a
'He's not the Messiah, he's a very naughty boy' T-shirt.
The teller asked me what it meant - and I said it was just a quote from an old comedy film.
She then said 'what's a Messiah? I thought that was an African tribe.'
AIBU to be surprised at someone (who by her accent I would assume had been brought up in the UK) who doesn't know the word Messiah?

Happy to be told my expectations are too high.

@FloralBunting Indeed! One of mine sung Handel’s Messiah with the BBC Symphony Orchestra at the Southbank. That was a state comprehensive choir.

Sorry if my opening post wasn't clear.

I was simply surprised that someone didn't know the word 'Messiah' (regardless of the context).

I wasn't surprised (and would not think it worthy of comment) that someone didn't 'get' a Monty Python quote.

"There's a mess alright, but no Messiah" is a common utterance in my house.