紫茉莉four-o'clock

为什么英文叫 four-o'clock ？
这里面肯定很有意思，请大家指点

Geoger 1 the four o'clock train this afternoon we have at four o'clock in the afternoon I don't think it's four o'clock yet. ( )lf l leave the school at four o'clock ,l can _home in time. Ican do my homework at four o'clock(一般，肯回） 是怎样做的 Lulu always gets up at six o'clock(用at six o'clock) It's five o'clock.I must____. It's twelve o'clock. 怎么问？ It's eleven o'clock 是什么时间？？？ IT's nearly seven o'clock,Jack___get home