Þrinnr

As defined by the Cleasby & Vigfusson Old Norse to English dictionary:

þrinnr

= þrennr, like tvinnr for tvennr; sinn, þrinnum, Rekst.

Possible runic inscription in Younger Futhark:ᚦᚱᛁᚾᚾᚱ
Younger Futhark runes were used from 8th to 12th centuries in Scandinavia and their overseas settlements