assertyoudaoicibaDictYouDict[assert 词源字典]
assert: [17] Assert comes ultimately from Latin asserere, which meant literally ‘join oneself to something’. It was a compound verb formed from the prefix ad- ‘to’ and serere ‘join’ (source of English series and serial), and it came to take on various metaphorical connotations: if one ‘joined oneself to’ a particular thing, one ‘declared one’s right to’ it, and if one ‘joined oneself to’ a particular point of view, one ‘maintained’ it, or ‘claimed’ it.

The verb was used in both these senses when English acquired it, from the Latin past participial stem assert-, but the former had more or less died out by the end of the 18th century.
=> serial, series[assert etymology, assert origin, 英语词源]
assert (v.)youdaoicibaDictYouDict
c. 1600, "declare," from Latin assertus, past participle of asserere "claim, maintain, affirm" (see assertion). Related: Asserted; asserting. To assert oneself "stand up for one's rights" is recorded from 1879.