Some functions from other spreadsheet programs don’t work in Sheets, but are reserved as built-in function names. One implication of this is that you cannot create named functions with these names.

CALL
CUBEKPIMEMBER
CUBEMEMBER
CUBEMEMBERPROPERTY
CUBERANKEDMEMBER
CUBESET
CUBESETCOUNT
CUBEVALUE
INFO
REGISTER.ID
RTD
WEBSERVICE

Each of these functions returns #NAME? with the error text:

This function is not fully supported in Sheets. Please see the help center for more information.