Why is there no U in forty?

[Panic Button]

Surely there should be

[Panic Button]

We can probably blame Shakespeare for that one.

[Quizmonster]

For pretty much the same reasons as I've already outlined, Factor. There's a 'v' in five but an 'f' in fifth, too.
As it happens, in Old English, twelve was written as twelf and twelfth as twelft. In the 14th century, the latter became twelfth to chime with the other 'th' endings...fifth, seventh etc. Twelve itself was spelt with a 'u or a 'w' in second-last place from the 12th...would you believe it?...century, but is recorded nowhere specifically with a 'v' before the late 14th century.

[kia cat]

Quizzy - you are a true genuis. I've always loved reading your posts.

[Quizmonster]

Oh, you're being much too kind, Kia Cat! But my thanks for your pleasant comment.