Lf
Everything has its origins in the Torah? Chanukah time there was a discussion regarding the min hag of giving Chanukah gifts, clearly a minhag borrowed from goyim (the discussion was wether this neccesarily made it assur) do you believe this too Automaticly has a source in the torah, after all it is included in everything. Others pointed out the minhag of trees in shul on shavuos, something the gra felt was assur as it is borrowed from goyim. Too bad he didn’t know where to look chas
There is such a thing as adopting goyish minhagim. If you can’t find an early source for it, (and I sincerly hope you do since unlike most people doing it today it actually is a family minhag of mine). It is reasonable to conclude that it is a recent innovation and given the similar earlier custom among goyim. It is reasonable to conclude that we adopted it from them.