The thistle mistletoe formula is a pagan Norse Runic formula, involving several rhyming words ending in -istill (typically at least þistill and mistill; thistle and mistletoe). The formula is attested in around 15 variants from the Viking Age.
Attestations
Ledberg stone (Ög 181) The Swedish Ledberg stone from Östergötland contains the formula. Following a standard memorial inscription, we read
When resolved becomes, in normalized Old Icelandic spelling:
Gørlev stone (DR 239) Likewise, the Danish Gørlev stone contains the exact same formula, along with a younger futhark rune-row.
Saga of Bósi The formula reaches its climax in a riddle in the legendary Icelandic Saga of Bósi and Herraud, where it reads (from manuscript AM. 586 4:0, transliterated into the Latin alphabet):
r.o.þ.k.m.u. iiiiii. ssssss. tttttt. iiiiii. llllll
Resolved and normalized, we get:
The meaning of the final word, uistil (vistill), is unclear.
References