With regard to slavish: Not unexpected. Except for a few nationality terms (
Danish, Polish), I think only the lax forms of the vowels
a,
e,
i, or
o are ever used in a stressed syllable before final
-ish (or
-ic or
-id). (
radish, perish, finish, Spanish, polish, ...) (
u is always tense in such words:
music, mulish, humid)
ks for
sk is a common substitute, if you ax me.
CJ