pre是前缀 表示先前的 预先的
known 知道的
pre-known 预先知道的
在这里应该是指已识别的设备
这类词叫做合成词 含义既然都知道 就是根据上下文选择最确切的翻译
在网上看到这段话：
"Used with the retrieveDevices() method to return those devices that are defined to be pre-known devices. Pre-known devices are specified in the BCC. These are devices that are specified by the user as devices with which the local device will frequently communicate."
pre-known devices指用户已经确认会经常与本地设备传递信息的装置.