[Opinions] It may or may not be unpronounceable in Japanese but
that doesn't really enter into it. Only abbasdaughter can answer this question, I suppose, but given that she's posting from Japan (see her profile), it certainly seems to make sense that the abbreviation used meant Japanese. The OP says the child's father is not Japanese. Who knows how they pronounce it or why they picked it. I'm just saying "Jpns" must in this context mean Japanese.