4 Answers

synonym |?sin??nim|
noun
a word or phrase that means exactly or nearly the same as another word or phrase in the same language, for example shut is a synonym of close .
• a person or thing so closely associated with a particular quality or idea that the mention of their name calls it to mind: the Victorian age is a synonym for sexual puritanism.
• Biology a taxonomic name that has the same application as another, esp. one that has been superseded and is no longer valid.
DERIVATIVES
synonymic |?sin??nimik|adjective,
synonymity |?sin??nimit?|noun
ORIGIN late Middle English: via Latin from Greek sun?numon, neuter (used as a noun) of the adjective sun?numos, from sun- ‘with’ + onuma ‘name.’

surrogate word

Yes there is, it is poecilonym

equivalent