The first part was English, the second Polish
Wrong assumption. Not having much contacts with spoken English language people tended to "rationalize" the pronounciation of the abbreviation read
in foreign magazines, "i" in hi
gh is pronounced "aj" (in Polish transcription), while in in "fi
delity" it's just an "i" (again in Polish transcription).
Btw, do foreign visitors to Poland travelling by train even care how we pronounce for example "PKP" (peh - kah - peh), or do they read it in their own language (or in English, as pee-kay-pee)?