There is this single word that is somehow still suck in my dictionary.?

Wait for it and I thought this word was obsolete millions of years ago.Ocay my queastion is why do some people say whilst when they mean while. Like comist to me they are welcomest to me and amongst I thought we left 14th words and put them in a obsolete bin.but some people believe it or not still say whilst.WHILST is a word that you say everyday.just joking.