I recently read Åsa Larsson’s The Savage Altar, translated into English from the original Swedish. It was a perfectly Scandinavian murder mystery, and for the majority of the book I did not notice it was a work in translation. There was one thing that kept tripping me up as I read:
For me, pee is used as a verb (‘she needed to pee’), while wee works much better as a noun (‘she needed a wee’), but can also work as a verb (‘she needed to wee’).
My hunch is supported by the Google Ngram data, using the handy tagger for part of speech, which shows the noun use of pee trailing verb pee significantly. (Usage note, when you search just in the British English corpus the use of pee falls off entirely, but the book was written with American usages throughout.)
I’m not entirely sure I would have noticed this so much if the book wasn’t a translation, or if there wasn’t the repetition of the usage. There are at least six uses of ‘a pee’ in the book, but there is also a use of verb pee, which sits much better with my intuitions (‘she needed to pee again’).
Historically, the Oxford English Dictionary has a citation for the verb form of pee from 1788, almost a century before the first noun usage in 1880. There may be some regional variation to this that I’m not aware of. I definitely grew up with Australian English wee, in both noun and verb form instead of pee. Both of these forms have a much more recent history, verb wee is first attested in 1934 and noun wee in 1968, and are considered British forms by the OED.