Thingy, whatsit, whatchermacallit - there are loads of these words. “Jawn” may have slight differences in the way that it is used when compared with “whatsit”, but it doesn’t seem very different. “Dongle” used to be used this way (by the person who invented the copy-protection dongle, who then repurposed the word). And then there’a the old faithful Latin “re”.