দহরম মহরম

No. While 'Maharam' comes from the name of an Islamic month, the idiom itself is completely secular and used by everyone regardless of religion.

You can, but it describes their 'closeness' and 'constant togetherness' rather than their 'love.' It’s more about them being a 'team.'

In an informal email to a colleague or friend, yes. In a formal business proposal, no—use 'collaboration' or 'relationship' instead.

There isn't a direct rhyming opposite, but you could say 'দা-কুমড়ো সম্পর্ক' (Da-kumro somporko), which means a relationship like a knife and a pumpkin (hostile).

In modern Bengali, no. It is an 'echo word' created solely to rhyme with and emphasize 'Maharam.'

It is usually transliterated as 'Daharam Maharam' or 'Dohorom Mohorom.'

It is equally common in both regions and is a staple of the Bengali language.

Usually, it refers to two people or two groups/parties. It’s rarely used for a large crowd.

Not at all. It’s a standard idiom. However, it can be used sarcastically to imply someone is being 'too friendly' for a reason.

Yes! If you have two cats that are always playing together, you can say 'ওদের মধ্যে খুব দহরম মহরম!'