Etymology

From Old Norse þorn, Proto-Germanic *þurnuz ‎(“thorn, sloe”), from Proto-Indo-European *trnus, *tr̥nom < *(s)tern- ‎(“thorny bush, thorn”), a variant of the base *(s)ter-, *(s)terə- ‎(“rigid, stiff”). Compare Norwegian Bokmål torn, Danish torn, Icelandic þyrnir, Dutch doorn, German Dorn, English thorn.