noun
good news; favorable information
Formal or literary term for news that something has gone well or turned out favorably. Often used in written correspondence or announcements.
吉左右が届き、一同安堵した。
Good news arrived, and everyone was relieved.
noun
news of an outcome; report on how something went
Formal/literary term for news about whether something succeeded or failed. Can be neutral, but often implies awaiting a result.
選考の吉左右を待つばかりだ。
We can only wait for news of the selection outcome.
便り is a common word for 'letter' or 'news from someone', whereas 吉左右 is more formal and focuses on the result of an event.
The exact derivation is uncertain. The kanji 吉 (good fortune) and 左右 (left and right, implying control or outcome) combine to suggest 'news of a favorable outcome'.