"fee to secure services," mid-15c., originally "act of keeping for oneself" from retain, or perhaps from or influenced by Middle French retenir, infinitive used as a noun. Meaning "fee paid to an attorney to secure his services" is from 1818.
retainer (n.2)
"servant," 1530s, agent noun from retain (v.). Also "one who retains or holds" (1540s). Meaning "dental structure used to hold a bridge in place" is recorded from 1887.
例文
1. I found the gardener，a family retainer ，morosely surveying the scene.
私はこの庭師を発見した――家で長年仕えてきた召使いが、このシーンをしかめっ面して見つめていた。
2.Liz was being paid a regular monthly retainer .
リーズは毎月1件の前払金を得ている。
3.I 'll need a five-handred-dollar retainer .
500ドルの手付金を受け取ります。
4.The agency will pay you a monthly retainer .
この機関は毎月あなたに雇用金を支払います。
5.Her arrival had just been announced by the faithful retainer .