Os's stanza reads the mouth as the source of all language, a pillar of wisdom and a comfort to wise men, and a blessing and a joy to every warrior, a stanza that treats speech itself, rather than any object or animal, as the rune's subject, one of the more abstract images in the whole poem's sequence of concrete, physical things.
The reading of Os as mouth is itself a piece of Anglo-Saxon reinterpretation worth noting: the Elder Futhark's cognate rune, Ansuz, names a god, most likely Odin specifically in the continental and Scandinavian tradition, while the Old English poem's Os stanza describes the mouth rather than any deity, a shift scholars generally read as the Christian compiler of the surviving poem quietly setting aside a pagan divine name in favour of a homophonous but religiously neutral reading, os in Old English meaning mouth as well as carrying an older, otherwise obsolete sense close to the Norse ass, god. Halsall's critical edition treats this as one of the clearest examples in the poem of the kind of careful reworking a Christian scribe transmitting pre-Christian material might apply, keeping the rune's name and general association with speech, wisdom and oracular power intact while removing its most directly pagan content.