Old and young - ronyaku

Japanese: 老若 - ろうにゃく

〘Noun〙 ("nyaku" is the Go-on pronunciation of "young")① Old people and young people. Old and young. Rojaku. ※Konpira Shrine Documents - February 2, 980, Tengen 3, a certain temple's assets ledger "Among the disciples, those who do not require the young and old to wear the official hakama and can become chief priests are selected and given the loyal seal as the Daihoshi, who has already graduated." ※Dangihon Furyu Shidokenden (1763), 5 "It is terrible that the young and old come to visit." ② Elders and young people of the Edo Shogunate. [Etymology] (1) It is a Japanese-style Chinese word that was mainly used in ancient records during the Heian and Kamakura periods, but "rosho," which is of Chinese origin and appears in documents from the Nara period, is more commonly used.
(2) The background to its formation is thought to be that the Japanese character "waka" had a meaning of "young," which did not originally exist in the Chinese character.

Rou-jaku lau... [old and young]

〘Noun〙 ("Jaku" is the Chinese pronunciation of "Waka") = Rounyaku (old and young) ※Kanmimimu (1908)〈Shibukawa Genji〉An interesting religious service "The shoulders of the whole family, young and old, were shook to the beat of the drum ."

Source: The Selected Edition of the Japanese Language Dictionary About the Selected Edition of the Japanese Language Dictionary Information

Japanese:

〘名〙 (「にゃく」は「若」の呉音)① 老人と若者。老幼。ろうじゃく。※金比羅宮文書‐天元三年（980）二月二日・某寺資財帳「御弟子中、不求老若、以吏袴堪者可為長吏也者、仍撰定附属忠印大法師既畢」※談義本・風流志道軒伝（1763）五「参(まゐり)の老若(ラウニャク)立つどひ」② 江戸幕府の老中と若年寄。[語誌](1)平安・鎌倉両時代には主として古記録などに用いられた和製漢語であるが、奈良時代の文献にすでに見える漢語出自の「老少」の方が多用されている。
(2)その形成には、日本語の「若」字に本来の漢語にはない、わかいの意が生じていたことが背景として考えられる。