Part time jobs in Japan or ... Arbeit

Part time jobs in Japan are called “arubaito”.
It is quite obvious that the word “arubaito” comes from the German word “arbeit” – meaning “work”, thought I am not sure why. Anyone knows why?
The hiring note in the image above calls for “arubaito” positions in a fast food chain restaurant. The salary is 850 to 970 Yen per hour. At today’s exchange rate that’s about 8.5 to 9.7 USD per hour.