This is has been discussed for a long time. You can check the "europe" file, which Paul said;

# From Paul Eggert (2018-10-03):
# As is usual in tzdb, Ukrainian zones use the most common English
spellings.
# For example, tzdb uses Europe/Kiev, as "Kiev" is the most common
spelling in
# English for Ukraine's capital, even though it is certainly wrong as a
# transliteration of the Ukrainian "Київ".  This is similar to tzdb's use of
# Europe/Prague, which is certainly wrong as a transliteration of the Czech
# "Praha".  ("Kiev" came from old Slavic via Russian to English, and
"Prague"
# came from old Slavic via French to English, so the two cases have
something
# in common.)  Admittedly English-language spelling of Ukrainian names is
# controversial, and some day "Kyiv" may become substantially more
popular in
# English; in the meantime, stick with the traditional English "Kiev" as
that
# means less disruption for our users. 
# controversial, and some day "Kyiv" may become substantially more
popular in
# English; in the meantime, stick with the traditional English "Kiev" as
that
# means less disruption for our users.