英语词源字典 - 在线词源网站

immaturity (n.)[immaturity 词源字典]: 1530s, "untimeliness," from Latin immaturitatem (nominative immaturitas) "unripeness," from immaturus (see immature). Meaning "lack of maturity" attested from c. 1600.[immaturity etymology, immaturity origin, 英语词源]
time-line (n.): also timeline, 1876, from time (n.) + line (n.).
untimely (adj.): 1530s, "coming before the proper or usual time," from un- (1) "not" + timely (adj.). Similar formation in Middle Danish utimelig, of weather, etc. Old English had untidlic "unseasonable." Related: Untimeliness.