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)