Þvest

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

þvest

or þvesti, n. [no doubt akin to Ulf. ga-þwastian = to make fast, þwastiþa = το ἀσφαλές]:—prop. the fast or firm parts, the lean of the flesh, as opp. to the fat, the lean of a whale’s flesh, the flesh underneath the blubber of a whale, opp. to ‘rengi’ and ‘spik;’ at af teknu þvesti ok beinum, Vm. 107; þvest-slytti, blubber, Grett. (in a verse); the word is freq. in mod. usage.

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