Dynamic expression
Get the columnName , used in Lookup  
@concat('SELECT STRING_AGG(name,''', ',',''') as columnName from sys.syscolumns where id =object_id(''', first(split(item(),'_')) ,'''' ,')' )

Get the actual query , this will run on the Source side in Copy activity 
@concat( 'SELECT ' , activity('ColumnNamefromDB').output.firstRow.columnName , ' FROM ' , item())

The above expression will derieve the actual table name dbo.flightData from the staging table dbo.flightData_stg which we have a passed as an array ( image 1 on this reply )
@last(split(first(split(item(),'_')),'.'))