I've noticed that in some (all? most?) languages, ordinal for 1 and 2 are completely different (i.e., not derived) from corresponding cardinals:
English One/Two/Three vs First/Second/Third is a bad example, because "second" is a loanword; and in other German languages, only first one is different: Dutch: Een -> eerst, twee - tweede
Russian: odin, dva, tri -> pervyi, vtoroy, tretiy
Estonian: üks, kaks, kolm -> esimene, teine, kolmas
Has any research been done into it? I wonder what this condition could imply about proto-languages.