AD
Anno Domini, After Death, CE, Common Era
The origin is after the narrative. What narrative was this? It's THE narrative, to many. This is the narrative of Jesus. This was so important that they decided to start a new era after it, making this era after death* or AD.
*Yes, I know it's not actually "After Death" but it's so commonly misconceived as such that I put it in there as the definition. You understand the meaning still, right? Anno Domini is also available as a definition too, so don't fret!
きげんご
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
この原始人は、紀元後にようやくスランプをだっ出するまで、あせらずじっとたえていました。
This caveman just calmly waited until he could finally get out of his slump in Common Era.
力ずくでネジをしめるとななめになりやすいってこと、紀元後になるまで知らなかったんだよね。
I didn't know that the screw wouldn't go in straight if you do it forcefully until Anno Domini.
紀元前五十年から紀元後二十年の間に作られたとされるこの地域の土器に、同じようなフグの模様が見られるんです。
Similar Fugu patterns can be seen on local earthenware made between 50 B.C. and 20 A.D.