Base.h

#ifndef BASE_H
#define BASE_H

#include <map>
#include <string>
#include <iostream>
 
class Base{
public:
    const std::map<std::string, std::string>& m;
    Base(const std::map<std::string, std::string>& m_): m(m_){}
    void printHelloStatement()
    {   
        std::cout << "Hello " << m.at("Hello") << "!" << std::endl;
    }   
};

#endif

Derived.cpp

#include <map>
#include <string>

#include "Base.h"
#include "Derived.h"

const std::map<std::string, std::string> Derived::myM {
    std::make_pair(std::string{"Hello"}, std::string{"World"})
};

Derived.h

#ifndef DERIVED_H
#define DERIVED_H

#include <map>
#include <string>

#include "Base.h"

class Derived: public Base{
public:
    Derived(): Base(myM){}
    static const std::map<std::string, std::string> myM;
};

#endif

Derived2.cpp

#include <map>
#include <string>

#include "Base.h"
#include "Derived2.h"

const std::map<std::string, std::string> Derived2::myM {
    std::make_pair(std::string{"Hello"}, std::string{"Kitty"})
};

Derived2.h

#ifndef DERIVED2_H
#define DERIVED2_H

#include <map>
#include <string>

#include "Base.h"

class Derived2: public Base{
public:
    Derived2(): Base(myM){}

    static const std::map<std::string, std::string> myM;

};

#endif

main.cpp

#include <iostream>

#include "Base.h"
#include "Derived.h"
#include "Derived2.h"


int main(int argc, char** argv){
    Derived d;
    Derived2 d2; 
    d.printHelloStatement();
    d2.printHelloStatement();

}

All derived classes need to have a common functionality, i.e. to print some "Hello" statement. This common functionality depends on a map data structure. Unfortunately, each derived class needs a different map. And, because all derived objects of the same type need the same map, it can be static. And because it's static, the base class can just take a constant reference to it so that every instance doesn't have a copy and waste space.