In 1999, Shigetaka Kurita created 176 emoji as part of NTT DoCoMo's i-mode, used on its mobile platform.[25][26][27] They were intended to help facilitate electronic communication, and to serve as a distinguishing feature from other services.[6]
As in the title of the linked article, the earliest emoji are not from 1999, or 1997, but from 1988. I know, because I'm the guy that discovered them.
But, yes, they're emoji because they were created and named in Japan. The IBM set serves a different purpose and exists in a different context. But, they are both living happily alongside each other in Unicode.
The 1988 set at 16x16px is the same resolution as Unifont and UnifontEX emoji, though due to having Plane 0 and Plane 1 simultaneously, UnifontEX works better as an emoji font.
I also find it fascinating, though I would say that we're not as highly documented as you might think. Articles and information is deleted and edited out of Wikipedia every second of every day. Mostly due to disagreements about whether a source, citation, or reference is "verifiable enough". For example, the device I have in my possession on which I found these oldest emoji is not proof enough that they exist, at least according to Wikipedia's rules. And then there's the grey area of early 1990s to early 2000s when the internet was still growing but wasn't big enough to contain enough good references, and those links that it did contain are probably long gone. So there's a second set of things that can't go on Wikipedia. Anyway! I think we have a long way to go.
It's from Japanese, a wasei kango (和製漢語) formation using on-readings of Chinese characters: 絵 (e, "picture") + 文字 (moji, "script"). The 字 (read ji) is the same as in 漢字 (kanji, "Han characters") and ローマ字 (rōmaji, "Roman characters". Exactly parallel to a neo-Latin / neo-Greek formation like "pictograph" (Latin pictūra, "picture" + Greek γράφω / graphō, "write, draw").
漢字 itself originates from Chinese, where it is pronounced hànzì in Mandarin and hon3 zi6 in Cantonese. It is also used in Korean, where it is pronounced hanja.
In Chinese, 絵文字 is orthographically borrowed as 繪文字 (traditional) / 绘文字 (simplified) — 繪, 絵 and 绘 all being alternate renderings of the same character. It is pronounced huìwénzì in Mandarin and kui2 man4 zi6 in Cantonese, according to the etymology of its constituent characters. In Korean it is borrowed phonetically as 이모지, imoji.
"Emoji" (絵文字) is also a false-friend for "Emoticon". "Emoticon" indicates icons that express emotions (typed with ASCII characters), but "Emoji" is simply the Japanese word for pictograph, and is not derived from the word 'emotion'.
https://en.wikipedia.org/wiki/Code_page_437