Poland, I think, though the Russian ending - ovski, or -ovsky is almost the same. I don't think the first "k" is part of it though - I recall a Paulowski at school, for example.
-ov is a suffix meaning "son of ---" or "of the --- family" in the Slavic languages. In Polish it's spelled with a W but it's still pronounced V. In Russian, final voiced consonants are usually rendered unvoiced, so it's pronounced -of, and since Russian uses a different alphabet we often transliterate it as -of or -off instead of -ov, as in Romanoff. Sometimes it comes out as -ev or -ew, as in Khrushchev or Zbigniew. The feminine suffix is -ova. In Czech, it's added to a woman's surname, so if her father's or husband's surname is Škoda, hers will be Škodova. -ski is a more general suffix used to form adjectives such as nationalities, e.g., Russki, Americanski. But it's also used in surnames with the general meaning, "descended from," usually appended to the -ov/-ev or -ow/-ew that's already there, such as Chaikovsky or Paderewski. But we occasionally see a name like Chomsky. We often see Chaikovsky spelled "Tschaikowski" because that's how the Germans have to spell it in order to pronounce it correctly.
So Mankowski, for example, translates to 'Descended from the family of Mank,' roughly? And Janikowski to 'descended from the family of he who has been favored with a son?'