eastern: on the side toward the sunrise, used above all of the east gate and of the eastern sea
Israelites got their bearings by facing the sunrise, so their direction words are built from the point of view of a person turned east. This adjective labels whatever lies that way: the gate on the east side of the temple, the sea along the eastern edge of the land.
Most of its spatial uses are close to fixed expressions. Ezekiel names the temple's eastern gate with it, the gate the glory of God leaves through when the city is abandoned. Three prophets use "the eastern sea" as a standing name for the Dead Sea, always set against the western sea, the Mediterranean, so that the two together mean "from one edge of the country to the other".
The same word also reaches into time, because for someone facing the sunrise what lies in front is both the east and the days that came first. The noun it is built from (קֶדֶם) does exactly the same double duty, meaning both "east" and "long ago".
Nuances
Whether the paired words in Job 18:20 name western and eastern peoples or later and earlier generations.
- majorityThe pair is spatial: those in the west are appalled and those in the east are seized with horror, a way of saying that everyone everywhere reacts.; E. Dhorme, A Commentary on the Book of Job; D. J. A. Clines, Job 1-20 (Word Biblical Commentary 17); HALOT, s.v. קַדְמֹנִי
- minorityThe pair is temporal: those who come after are appalled and those who went before are horrified, a way of saying that every age is shaken.; BDB, s.v. קַדְמֹנִי