Okkr

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

okkr

dat. and acc. dual, [Uif. ugk, ugkis = ἡμας, ἡμιν]:—us, of two, in countless instances; the old writers make a strict distinction between dual and plur. (okkr oss, ykkr yðr, vit vér), whereas mod. Icel. in the spoken language has exclusively adopted the dual; thus Icel. say, hann sagði okkr, hann bað okkr; this use of the dual for the plur. is prop. a familiar way of speaking, regarding the speaker himself as the one, and ‘the rest’ as the other person; in writing the old distinction is still often observed.

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