A "placeholder name" is a temporary or generic name used to represent something or someone when their actual name is not known or does not matter. It is like using a temporary label until the real name is discovered or provided. Full definition
If you decide to leave the hospital without naming your baby, the state may automatically give the child a legal placeholder name, such as «baby boy.» (howtoadult.com)
FlyToo is a temporary placeholder name by parent company Enerjet. (moneysense.ca)
Since then, Lane and team have continued to discover more Borrelia species in California's coastal range, including B. miyamotoi, the cause of a relapsing fever; B. californiensis; and «Borrelia genomospecies II,» a placeholder name until the species is fully described. (discovermagazine.com)