The phrase "uncertain origin" means that the source or starting point of something is not known for sure.
Sentences with «uncertain origin»
They were long and elegant (as they should be), but they were of uncertain origin. (bookbrowse.com)
He is unhappily married to Aislin (Andrea Riseborough), a blow - in of uncertain origins who appears to be a covert pantheist, even a witch. (independent.ie)
Often, found objects are used, with a sometimes uncertain origin — such as portrait busts, which are hewed until their recognisable facial features completely disappear and they assume the character of fossilised silhouettes. (artlead.net)