It is indeed a loanword, though from Arbeit, not Arbeiter. Japanese uses it too. English is FAR from being the only language to loan words to other languages, and is of course famous for importing words greedily itself, as Jame D Nicoll famously said:
“The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don't just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary.”
― James D. Nicoll
