It is actually more helpful to examine the same word in Job 9:9 where other constellations are also mentioned but their precise identification is not certain. One can only say that because the translators of the LXX were more than two thousand years closer to the ancients, and better understood the surrounding mythology (from which these ancient names are derived) they might be better placed to understand them.
Note the comments by the Cambridge Commentary in Job 9:9
- The Hebrew names are ‘âsh (‘ayish ch. Job 38:32), keseel, and keemah. These names may possibly denote the Bear, Orion and the
Pleiades or seven stars; there is, however, considerable uncertainty.
The word keseel means “fool,” which is to be interpreted as the Syr.
and Chal. in this place, giant, cf. Genesis 6:4, that is, some
heaven-daring rebel, who was chained to the sky for his impiety. Such
mythological ideas belong to a time anterior to authentic history,
though as still lingering in the popular mind they are alluded to in
such poems as Job. In Isaiah 13:10 the word is used in the general
sense of constellations. Keemah perhaps means heap, and is a natural
name for the Pleiades. Others have interpreted the expressions
differently (see Delitzsch Comment. p. 127).
the chambers of the south - are probably the great spaces and deep
recesses of the southern hemisphere of the heavens, with the
constellations which they contain. These being known to exist, but
only suggested to the eye, are alluded to generally.
The Pulpit Commentary makes similar remarks in Job 9:9
Verse 9. - Which maketh Arcturus, Orion, and Pleiades; literally,
which maketh 'Ash Kesil and Kimah. The rendering of the LXX. (ὁ ποιῶν
Πλειάδα καὶ Ἕσπερον καὶ Ἀρκτοῦρον), supported, as it is, by most of
the other ancient versions and by the Targums, has caused the stellar
character of these names to be generally recognized; but the exact
meaning of each term is, to some extent, still a matter of dispute. On
the whole, it seems most probable that 'Ash or 'Aish (Job 38:32),
designates "the Great Bear," called by the Arabs Nahsh while Kesil is
the name of the constellation of Orion, and Kimah of that of the
Pleiades. The word 'Ash means "a litter," and may be compared with the
Greek ἅμαξα and our own" Charles's Wain," both of them names given to
the Great Bear, from a fancied resemblance of its form to that of a
vehicle. Kesil means "an insolent, rich man" (Lee); and is often
translated by "fool" in the Book of Proverbs 14:16; Proverbs 15:20;
Proverbs 19:1; Proverbs 21:20, etc. It seems to have been an epitheton
usitatum of Nimrod, who, according to Oriental tradition, made war
upon the gods, and was bound in the sky for his impiety - the
constellation being thenceforth called "the Giant" (Gibbor)' or "the
insolent one' (Kesil), and later by the Greeks "Orion" (comp. Amos
5:8; and infra' Job 38:31). Kimah undoubtedly designates "the
Pleiades." It occurs again, in connection with Kesil in Job 38:31, and
in Amos 5:8 The meaning is probably "a heap," "a cluster" (Lee); which
was also the Greek idea: Πλειάδες, ὅτι πλείους ὁμοοῦ κατὰ μίαν
συναγωγήν (Eustath., 'Comment. in Hom. II.,' 18:488); and which has
been also inimitably expressed by Tennyson in the line, "Like a swarm
of dazzling fireflies tangled in a silver braid."