This is a little off-topic article. Someone wished me “Goodnight” and I wished them back “Good Night”. After looking a bit on the internet, I stumbled upon this amazing stuff – Google Books Ngram Viewer. This tool basically searches a comma-delimited search strings using an yearly count of n-grams found in sources printed from 1500. The most impressive part of the tool is that the resultant data of the search is converted into a frequency chart.
Now coming back to the dilemma, I wanted to know which one is correct — “Goodnight” or “Good Night”, and that is when I stumbled upon an EpiGuy’s answer on English StackExchange. That is where I got the reference to Google Books Ngram Viewer. Now according to EpicGuy and Google Books Ngram Viewer, “Goodnight” is something that has been used much more frequently in recent times. But the most commonly and correct convention is still “Good Night”.
Interestingly all the other joined time wishes like “Goodmorning” or “Goodevening” are not as much exploited as “Goodnight”.
Go ahead and get crazy with the Ngram Viewer and peek through the linguistic history 😉