where did the patterns on the straps of christ in leonardo's painting Salvator Mundi painting ogrinate from?

by bonbon64

Dont know if you guys saw leonardo's painting Salvator Mundi. But i was intrested in why he used two diffrent patterns in the painting. I could not find an origin to the pattern on the straps. It looks half celtic, half roman or maybe older?

Info from wiki: Artist Leonardo da Vinci - Born 15 April 1452, Died 2 May 1519 (aged 67) Year of painting c. 1490–1519 Type Oil on walnut Dimensions 45.4 cm × 65.6 cm (25.8 in × 17.9 in)

There has been quite a few link on social media about the painting today. I have quite a few questions. But the pattern i could not find. I wouldnt emagine he would make it up on the fly?

https://imgur.com/a/W8Vx1

bonbon64

I can see the pattern on the garment is celtic.