In its sole attestation the word disrupts the rhyme-scheme. The variant reading, while using an entirely different word, preserves the same rhyme-sound. It may be suggested that it is the previous line that is corrupt (and can easily be changed to ‘Deivent guarder al ciel’ to produce a rhyme) rather than this particular word.
The word, though unusual, is probably an early form of the adjective originel (see original), derived from the Latin verb oriri; cf. the commentary on orine1. The definition of ‘Pleiades’, confirmed by TL, can thus perhaps be explained either by the association of this star cluster with the beginning of summer and equinox (‘to begin’) or by the fact that they start appearing in the sky in July (‘to rise'). In the preceding context in Best (ll. 1257-61) the star is explicitly identified as Virgilia, which is a name traditionally associated with the Pleiades (cf. TL).
An alternative interpretation, suggested by the variant reading esteille jurnale (see esteille), would be that the term refers to the morning star, i.e. the planet Venus when it appears in the east before sunrise. Even though this seems to be the meaning that has to be attributed to the scribal variant, it must be incorrect in the present context.