I found records for my GGF POLLAK with different given names for various life events. This was Farkas POLLAK (born 1814) and his son (born 1846) in Zala county (SW part of Hungary), a German-speaking part of the A-H empire.
Based on the limited records I have; in 1846, he used the name Jozsef when recording his son's birth. Then in 1848, he used Farkas for the Jewish Census.
In 1855 and 1868, he used Wilhelm in his children's marriage registers. 1877, for his daughter Fani's (my GM) marriage, his name was Wolf. The 1901 death record for his daughter Fani showed Jozsef for her father.
A similar situation with Farkas' son; born in 1846, given name of Lipot, then in the 1848 census, he was named Samuel, then he was named as Izidor for all further records to his death in 1927.
Thanks for any ideas/comments ,
Ed Zwieback
Long Beach, California