It is interesting to see how Muslim forms of greetings have changed over the years, especially in the Indian sub-continent. Recently, I went for a classical music concert where the Ustad/ musician greeted the audience with Adaab (along with the usual Good Evenings, namaskars, etc).
Adaab means Hello in a very formal way, and is a polite form of 'secular greeting'. It is followed by a gesture where you take your right hand towards your forehead, with back of the hand showing and the palm spooning towards your face (unlike the Army salam, which is your palm outwards touching your forehead!). Adaab literally means 'etiquette'. Even non- Muslims who are connoisseurs of Urdu language, practice 'adaab' in their formal greetings (poets like Gulzar, late Anand Bakhshi, etc.). Tasleem is also very similar to Adaab as a form of greeting. Literally it means 'to accept'.
It is very rare to hear Adaabs/ Tasleems these days. Adaab and Tasleem are cultural greetings whereas Salam is religious. Salam means 'peace' (Assalamalaikum/ walaikum-as-salalm, literally meaning 'May peace be upon you'). Adaabs and tasleems have been taken over by Salam now amongst the Muslims. The new generation of Muslims may not even have heard of the previous forms of greetings.
Salam is Arabic and Adaab/ tasleem trace their origin in Urdu/ Persian tradition. The prevalence of Arabic Salam now, also points at the way Muslim identity is being constructed now, leaning more towards the larger Muslim 'Ummah'/ community. Adaabs and tasleems prevailed when the Hindu/ Muslim composite culture was at its height. Nowadays, Urdu is not the court/state language anymore. Thus the greetings which formed the bridge between the Muslims and non- Muslims, have been replaced by more casual 'Hello/ Hi', which also, points at the English languages' dominance in present times.
The form of greetings' reflect the prevalent norms and dominance of a particular language' in the society. Prevalence of Adaabs/ tasleems reflected prominence of Urdu, and importance of the Ganga- Jamuni tehzeeb (Hindu/ Muslim mixed culture). Religious identities are more sharp and more symbolic these days (Jai Mata Di, Har Har Mahadev, Jai Ramji, etc.) and therefore, Arabic Salam which stresses more on the universal identity of being a Muslim.
(Although, salam has a better literal meaning of wishing peace upon the other!)