I don't think there's an accent on the e in Panadeine Forte so different derivation?
There is no accent on the packet as far as I know. No idea where they derived it from, and I can't remember how the announcers pronounce it on their advertisements.
With no accent, the French pronounce 'forte' as
fort and the Italians pronounce it as
fore-tay. (In fact, Italians use no accents in their written language).
"Forte" in French primarily means
strong; it is an adjective and is actually - as spelt - in the feminine form, i.e. used to describe feminine nouns. The masculine form of the same adjective is "fort", which is pronounced
for (i.e. in French the final 't' is not pronounced unless the next word starts with a vowel sound). "Forté", which would be pronounced
fore-tay (except with a
very short 'ay'), doesn't appear to have any meaning whatsoever in French.
"Forte" in Italian primarily means
strong but it has been frequently used in music to denote a passage to be played or sung loud (or loudly, as opposed to "piano" meaning softly).
Dictionary.com gives the etymology of "forte" meaning someone's strength to the French, therefore strictly speaking the correct pronunciation is the monosyllabic
fort. However, if one is referring to the musical direction or annotation, it is intended to be pronounced as in the Italian and thus
fore-tay. It then goes on to say that due to the increasing misuse amongst the younger generation and likely due to the cross from musical education, both pronunciations are now considered standard for conveying someone's strengths.