beforehand (adv., adj.)youdaoicibaDictYouDict[beforehand 词源字典]
also before-hand, early 13c., from before + hand, which here is of uncertain signification, unless the original notion is payment in advance or something done before another's hand does it. Hyphenated from 18c., one word from 19c.[beforehand etymology, beforehand origin, 英语词源]