Surname Fiuk derives from:
1. Old Polish noun 'fiuk', a kind of pottage, soup
2. Old Polish verb 'fiukać', to whistle
fiuk - a dialectal noun meaning a whistle, from the verb 'fiukać' - to whistle.
fiukać - colloquially gwizdać, świstać - to whistle, to whiz, to swish
fiuki - plural of fiuk - little insignificant things; irrelevant matter. Example: "Tobie tylko fiuki w głowie" - You have only tiny things in your mind.
There are several villages in Poland derived from the name 'fiuk':
1. Fiuk, Gmina (municipality) Żabno, Tarnów County, Małopolskie (Lesser Poland) Voivodship
2. Fiuków, Gmina Krzywda, £uków County, Lublin Voivodship
actually there are two BORSZOWICE very close to each other
That's true, the two are only 38 km apart:
1. Borszowice, Gmina Imielno, Jędrzejów County, Świętokrzyskie Voivodeship, E of Jędrzejów
2. Borszowice, Gmina Sędziszów, Jędrzejów County, Świętokrzyskie Voivodeship, WSW of Jędrzejów
3. There was also Borszowice in Ukraine, Stary Sambor region, Lwów Province; Now Борше́вичі - село в Україні, Старосамбірському районі Львівської області.
St. Nicolas Parish Parish Imielno, Parafia Św. Mikołaja, 28-313 Imielno, ul. Kościelna 2
St. Peter and Paul Parish Sędziszów, 28-340 Sędziszów, ul. Kościelna 10
tel. 41-381-10-14, wik. 41-381-27-98
According to Geneteka, Świętokrzyskie Voivodship, there were 48 marriages of Fiuk grooms or brides, between 1800 and 1950, mostly in the following places:Imielno
, Piotrkowice, Jędrzejów
Similarly, there were 91 births during the same period at the same localities
Start here: geneteka.genealodzy.pl/index.php, select
None of these records point to Sędziszów.
I conclude that your grandfather was born in Borszowice, Gmina Imielno, as Roman-Catholic. The details are to be found in Imielno Parish.
Archiwum Państwowe w Kielcach (National Archive in Kielce) keeps mostly the 19th century records, but only few from 1900s, so I suspect that the remaining records are in Parish Imielno.
Just in case I missed something check this: