 in language is the day that people usually gather and meet each other
والعيد كل يوم فيه جمع, واشتقاقه من عاد يعود كأنهم عادوا إليه; وقيل: اشتقاقه من العادة لأنهم اعتادوه
"'Id also means the day that people usually gather together. 'Id comes from the word عاد يعود (repeating) because they routinely do it (get-togethers). Some linguists argue, the origin of the word from العادة (habits) because they used to do that "(Lisaanul 'Arab)
The Shari'a stipulates that 'Eid al-Fitr and Eid al-Adha are fun days. As told by Anas bin Malik Radhiallahu'anhu:
قدم رسول الله صلى الله عليه وسلم المدينة ولهم يومان يلعبون فيهما فقال ما هذان اليومان قالوا كنا نلعب فيهما في الجاهلية فقال رسول الله صلى الله عليه وسلم إن الله قد أبدلكم بهما خيرا منهما يوم الأضحى ويوم الفطر
"In the time of the Prophet sallallaahu'alaihi Wasallam just moved to Medina, the people of Medina had two feast days which usually on that day they had fun. The Prophet asked: 'What celebration is celebrated in these two days?' The Madinah replied: 'On these two feasts, in the days of Jahiliyyah we used to celebrate by having fun'. Then the Prophet sallallaahu'alaihi Wasallam said: 'Truly Allah has changed your feast day with a better one, namely Eid al-Adha and' Eid al-Fitr '(HR. Abu Daud, 1134, dishahihkan Al Albani in Sahih Abi Daud, 1134)
In a hadith of qudsi, Allah the Exalted says:
According to him, specializing the day to visit each other who live the same law as to specialize the day to visit the dead (pilgrimage to the grave). While specializing the day for grave pilgrimage is heresy. But this opinion seems inappropriate if we consider the reasons above. What is clear, this problem includes the ijtihadiyyah realm which we should be able to tolerate the opinions of the ulamas.o