These are builtin basic types in asn.1 .
From rfc 1157 snmp
:
[9] Information processing systems - Open Systems
Interconnection, "Specification of Abstract Syntax
Notation One (ASN.1)", International Organization for
Standardization, International Standard 8824,
December 1987.
[10] Information processing systems - Open Systems
Interconnection, "Specification of Basic Encoding Rules
for Abstract Notation One (ASN.1)", International
They did not put standard names - X208 and X209 . Search forum for ITU standards link and download those from there .