Well - answering the OP.
What I found with trying to write a song that would get folkies guessing about provenance was to do with "my style" and accuracy.

We all use words that we know. People who know, you know your lexicon to some extent. What you really need is to cull your "you" words and try to substitute ones that fit the genre/time/trade/etc.

Then there is accuracy - I once wrote a song about trees and assumed that Ash was a good wood for a longbow. It is but Yew is more likely and more likely to be known to the cognicentii. There is always someone who knows something you don't so listen to the pedant and do the research. Or do the research first. It can be tedious but how badly do you want to get it right?

As for the music - if you play a lot of trad music it will usually come out trad-ish.

One trick that gets the singer/wrongciter purist riled is to take an existing song, write new words then compose a new tune to the words. It will have a lot of the flavour of the original but - hey! Thats what you are aiming for.

I am sure you knew all this already - but it is nice to be reminded &/or have it confirmed.