infinitive (n.)youdaoicibaDictYouDict[infinitive 词源字典]
"simple, uninflected form of a verb," 1510s (mid-15c. as an adjective), from Late Latin infinitivus "unlimited, indefinite," from Latin infinitus (see infinite). "Indefinite" because not having definite person or number.[infinitive etymology, infinitive origin, 英语词源]