pastyoudaoicibaDictYouDict[past 词源字典]
past: [13] Past originated simply as a variant spelling of passed, the past participle of pass. The earliest unequivocal examples of it are as a preposition, but its adjectival use followed in the 14th century, and by the 16th century it was being employed as a noun too (the past).
=> pass[past etymology, past origin, 英语词源]
past (adj.)youdaoicibaDictYouDict
c. 1300, "done with, over," from past participle of passen "go by" (see pass (v.)). Past participle is recorded from 1798; past tense from 1813.
past (n.)youdaoicibaDictYouDict
"times gone by," 1580s, from past (adj.).