Thanks for asking. They come from the Mnemonic major system,.The letters were chosen because of they resemble the shapes of numbers, or have some other memorable connection. So there is nothing that is specific to English in that sense. Other European languages should be fine.
There would be some difficulty in using it for languages without a lot of consonants (Hawaiian and Polynesian languages). Also Arabic is missing a p and doesn't use g in a the same way as English, but this is okay because you have other b and k sounds to stand in for those. L and R might not be as distinct in Japanese and Korean. In that case, the L/R sound could both be assigned to 4, and other sound like h or y could be assigned to 5.